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Comment on Organisational Disclaimers

29 марта, 2020 - 10:28
Published on March 29, 2020 7:28 AM GMT

[This post has been sitting in my drafts since I first wrote it. I'm publishing it with minimal polishing for Daniel's Blog Post Writing Day II. Sorry that it's not as clear as it could be.]

A while back I was chatting with someone about representing themself and their organisation on the internet - they're someone at an org in the EA/Rationality professional network who sometimes comments on various public online platforms. They were encouraging a colleague at their org to include a few sentences of disclaimer to tell everyone that they're not speaking on behalf of their org and that they're speaking for themselves.

Here are some messages I wrote back:

I think there's something weirdly formal and slightly bad about the way most people write those sorts of sentences, but I've not been able to put my finger on it.

I think people often signal something like "You're supposed to pretend to not believe things about my organisation as a result of things I say here", and that's often not quite true, because if you're in the core 5-10 people or something it actually is evidence, but you don't know if it's a consensus view in the org. 

I think folks should try to say something more like "The causal process behind my comment/post is I wrote down my thoughts and answered in a way that is representative of my thinking. I did't run this past my colleagues, I'm not actually sure what they think, and I'm not trying to report consensus views here."

They replied

I think you've hit the nail on the head with why I've always disliked those 'I'm speaking in my personal capacity' comments – it feels like it's requesting that we pretend not to update on something that by all rights has to be evidence

And it feels sort of contentless or like it's allowing too many interpretations

Whereas 'I didn't run this by my colleagues' feels like an excellent thing to say, and perfectly reasonable given how costly it is to run everything you publicly say by everyone at your org!

I explicitly recommended against it and against anything that sounds like boilerplate 

not least because once you start doing that, you have to do it all the time (because otherwise any comments without that caveat implicitly are things your employer thinks??)

... also the idea of orgs 'having opinions' strikes me as very slightly metaphysically problematic

Let me use an example that's on LessWrong. Vaniver, in his brilliant post Public Positions and Private Guts, has the following disclaimer:

[Note: the concept for this post comes from a talk given by Anna Salamon, and I sometimes instruct for CFAR, but the presentation in this post should be taken to only represent my views.]

And I actively feel a little lurch reading it, because when I read "should not" I feel like I'm supposed to go along with the claim under social pressure ("you should not show up late to work") but the thing I'm being told I should not do is to not believe something that is bayesian evidence – when it clearly is. I should indeed take the post to have some representation of the other person's views, because this post was inspired by them. 

I think the truth here is that when Vaniver wrote the post he was trying to write his own perspective, he wasn't trying to faithfully represent Anna's, Anna probably didn't give much feedback on the post, and all of the consequences of this state of affairs. This is a more accurate description to me.

...I feel like I should try to offer an alternative here.

My current plan is to mostly just talk for myself, and try to signal deviations from this clearly (which I expect to be rare). I think this equilibrium mostly works out, though there's been a few times it's not quite worked out great, and I might change to adding lots of disclaimers. But for now I'm still holding onto the hope that I can stick to the equilibrium where I just write off-the-cuff thoughts on the internet all the time without disclaimers.

I replied in the conversation above:

I mostly have always just been speaking for myself at LW. The main problem I've run into is, when I obviously always say "I think" and never "we think", and am just speaking the same as normal, people have made the false assumption that I'm speaking on behalf of the team or the mod team or something, so I have updated on the need to solve this even though I am against disclaimers. 

I have been thinking about making sure it's easy to create very blunt common knowledge of when I am trying to speak from consensus (e.g. might make mod comments a different colour or something) so as to throw into relief all the other comments.

But I know some people feel they're in an equilibrium with a strong expectation that they're speaking for the org, and so feel a constant need to disclaim. In which case, I will try to helpfully offer what I think is a more truthful disclaimer:

I wrote this comment from my perspective, I'm speaking for myself, and am not attempting to represent a consensus at any organisation I'm connected to.

That's the simplest one. If you'd like something more general, you could try this:

I write comments from my own perspective, and am speaking for myself. When I write comments, I don't try to represent organisations I'm connected with, other than when I explicitly say that's what I'm doing.

I'm not sure these are clear and snappy enough to get widely used, but they do feel to me more like they're true, which I like.

I think one of the reasons is that I basically don't think anyone should be writing in an official capacity in their own account. I mean, they should sometimes, but they shouldn't do it here on LessWrong. We're not that kind of place. Don't make accounts where the name of the account is the name of your organisation. I want to speak to individuals, not faceless entities. I don't mean to say that writing in the passive voice isn't acceptable, or that the person should always be front and centre, just that most of the ways orgs do this are pretty bad for clear and open discourse.

I think the correct thing is to just state clearly that you're not attempting to represent anyone's perspective other than your own. It's easy for readers to make the correct inferences about how representative the comment is about you and your orgs once they have this information about how you wrote the comment.

I do think that my alternatives will feel to many people like it doesn't sufficiently distance what they wrote from the organisation - they want to make sure that nobody forms beliefs about the organisation from that comment. Unfortunately, I think that's not a fair expectation to ask of others, because you really do work at that org, this is a real thought you had, and it's actual bayesian evidence about how you think and about what decision-making is like in the org.

I think it's basically still pretty fine to write such things publicly. I mean, if you think that your org cannot survive people knowing the random sh*t its staff say in their off-hours, then that's a problem. It either means that working with the org is incompatible with freely speaking in public which is a red flag, or it means you need to talk within your org and make a plan to have a clear space for the org to speak for itself so that people are able to build good and clear separate models.

Related thought: I think it's important when you're considering being hired by an org, to ask yourself whether the org will put these kinds of constraints on you, and weigh it as a factor. Such restraints are both common and very strong and will hold you back from (not to speak too grandly) contributing to and engaging with the accumulation of knowledge and the broader process of science. Make sure you're still able to think for yourself in public.



Discuss

Today's Online Meetup: We're Using Mozilla Hubs

29 марта, 2020 - 07:00
Published on March 29, 2020 4:00 AM GMT

That's right! Tomorrow/Today (Sunday Mar 29th) we're having an online LessWrong meetup in Mozilla Hubs. You're welcome to join and chat with some of the interesting people who read LessWrong, SSC, Overcoming Bias, and so on. I am personally quite excited to talk with a bunch of you.

At 12 noon PDT we'll be having the Hanson/Mowshowitz "Expose The Youth" Debate, then after that at around 2pm we'll having a post-debate meetup. This an experiment, I'll do it more if it's fun.

Basic controls:

  • WASD to move
  • G to toggle flying
  • Click and Drag to look around
  • You can hear and be heard by people in proportion to how close you are to them

The rules:

  • Only 25 people can be in a room. Move around and check out the other rooms!
  • Login as soon as you arrive and use either your real name or a standard alias like your LessWrong username. I'd like some basic accountability please, and today I will remove people who don't follow this rule.
  • Being weird is positively fine and I don't think you have a limited budget to spend, you can just be super weird. But if you're too loud and if people are having a bad time because of your presence, a moderator will remove you from the rooms.

I've made a few basic rooms. If you've not visited before or need some help, enter one of the tutorial rooms. Here's the first:

All four are here: Tutorial 1, Tutorial 2, Tutorial 3, and Tutorial 4. Please leave the tutorial rooms once you've solved your problems, to make space for others.

And here are the hangout rooms.

Extra rooms in case you want them for whatever reason: Don't Touch the Floor.

As a reminder, here's the debate livestream:



Discuss

"No evidence" as a Valley of Bad Rationality

29 марта, 2020 - 02:45
Published on March 28, 2020 11:45 PM GMT

Quick summary of Doctor, There are Two Kinds of “No Evidence”:

  • Author has a relative with cancer. Relative is doing well after chemo and is going to a doctor to see if it's worth getting more chemo to kill the little extra bits of cancer that might be lingering.
  • Doctor says that there is no evidence that getting more chemo does any good in these situations.
  • Author says that this violates common sense.
  • Doctor says that common sense doesn't matter, evidence does.
  • Author asks whether "no evidence" means 1) a lot of studies showing that it doesn't do any good, or 2) not enough studies to conclusively say that it does good.
  • Doctor didn't understand the difference.

Let me be clear about the mistake the doctor is making: he's focused on conclusive evidence. To him, if the evidence isn't conclusive, it doesn't count.

I think this doctor is stuck in a Valley of Bad Rationality. Here's what I mean:

  • The average Joe doesn't know anything about t-tests and p-values, but the average Joe does know to update his beliefs incrementally. Lamar Jackson just had another 4 touchdown game? It's not conclusive, but it starts to point more in the direction of him winning the MVP.
  • The average Joe doesn't know anything about formal statistical methods. He updates his beliefs in a hand-wavy, wishy-washy way.
  • The doctor went to school to learn about these formal statistical methods. He learned that theorizing is error prone and that we need to base our beliefs on hard data. And he learned that if our p-value isn't less than 0.05, we can't reject the null hypothesis.
  • You can argue that so far, the doctors education didn't move him forward. That it instead caused him to take a step backwards. Think about it: he's telling a patient with cancer to not even consider more chemo because there is "no evidence" that it will do "any" good. I think Average Joe could do better than that.
  • But if the doctor continued his education and learned more about statistics, he'd learn that his intro class didn't paint a complete picture. He'd learn that you don't always have access to "conclusive" evidence, and that in these situations, sometimes you just have to work with what you have. He'd also learn that he was privileging the null hypothesis in a situation where it'd make sense to do the opposite. The null hypothesis of "more chemo has no effect" probably isn't true.
  • Once the doctor receives this further education, it'd push him two steps forward.
  • In the intro class, he took one step backwards. At that point he's in the Valley of Bad Rationality: education made him worse than where he started. But then when he received more education, he took two steps forward. It brought him out of this valley and further along than where he started.

I think that a lot of people are stuck in this same valley.



Discuss

Will grocery stores thwart social distancing, and when should I eat my food stockpile?

29 марта, 2020 - 01:50
Published on March 28, 2020 6:20 PM GMT

I live in Boston. From what I am hearing, grocery stores are mobbed, day after day, and don't seem to be taking social distancing seriously. Is this a serious enough problem to keep R0 above 1, and prevent successful suppression?

I have about a 4-week supply of food but I want to save it for the worst 4 weeks of the pandemic. I will take my chances with delivery/the local convenience store until then, both of which involve lower exposure risk than the grocery store by 1-2 orders of magnitude. According to some projections, the worst 4 weeks are about to start. But that seems extremely optimistic to me. My naive expectation was that without social distancing the peak would be in June. Distancing should reduce how bad the peak is, but also extend it, assuming distancing is not sufficient to lower R0 below 1.

I can extend the life of the stockpile if Amazon Fresh ever becomes operational again. This involves non-zero risk, but one delivery a month from them is much less risky than daily uber eats/convenience store runs.

In an extended-peak scenario it doesn't really matter when I eat the stockpile because I am going to have to get at least some deliveries during the peak. But in a high and short peak scenario, both my ability to avoid all deliveries and the desirability of doing so are a lot higher. In a low and short peak (i.e. successful suppression), the desirability of avoiding all deliveries is less, but I maintain the ability to do so and I might as well, if I can predict it correctly.



Discuss

Rob Bensinger's COVID-19 overview

29 марта, 2020 - 00:47
Published on March 28, 2020 9:47 PM GMT

Robby posted this to Facebook on March 15th, and just updated section 2 and 3 with new information, making this I think currently one of the best guides to how to respond to this whole situation. 

If you live in the US, I recommend that you self-quarantine immediately (to the extent that's possible for you) to avoid exposure to COVID-19, the new coronavirus disease. I'll explain why below, then give tips on how to reduce exposure and what to do if you get sick.

Quarantine isn't all-or-nothing, and every little bit helps. Even if you expect to catch COVID-19, you're likely to get sicker if you're exposed to more viral load early on.

(Paul Bohm says "pretty much any viral/bacterial dose study shows that result". Divia Eden: "As I understand it, the virus replicating is an exponential process, and antibody production is an exponential process too. So an early difference in load should make it easier for the latter to outpace the former." This may be why medical staff who were infected while treating COVID-19 patients have seen some of the worst outcomes.)

So even if you can't (e.g.) work from home right now, I would still recommend taking large measures to reduce your exposure.

I expect things to get increasingly dangerous over the next few weeks, so I'd especially recommend taking action now to reduce the amount you're likely to be exposed between end-of-March and end-of-May. By default, risk of exposure doubles every few days until the pandemic peaks.

Disclaimer: I am not a doctor or an epidemiologist.

 

1. Why I think you should self-quarantine

[Section omitted from the crosspost, since most people appear to understand the importance of self-quarantine by now. The section can still be found here]

 

2. Ways to reduce risk now:

A. Avoid people.

The CDC (https://www.cdc.gov/coronavir…/2019-ncov/…/transmission.html) believes that COVID-19 is mainly spread person-to-person, "between people who are in close contact with one another (within about 6 feet) through respiratory droplets produced when an infected person coughs or sneezes. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs."

Given that asymptomatic transmission seems common, talking is also probably a common vector -- you'd be surprised how much spit flies when people talk.

So my top recommendation is to avoid being near other people (unless you're self-quarantining together), especially in crowded or indoor spaces.

(Added Mar. 16, from Michael Keenan: "Starting at midnight, all non-essential work and movement outside homes is banned in Alameda county and most other bay area counties. Grocery stores and pharmacies will remain open, and restaurants may still do takeout food (and presumably delivery), for those who are still using that." Similar measures may be taken elsewhere in the US soon; be prepared for the possibility.)

 

B. If you do need to be around people, wear something over your mouth and nose.

Be sure not to touch/adjust the mask/covering (or your face) while wearing it, except to take it off (and throw it away or sanitize it) when you're done using it.'

I've heard some people claim masks aren't useful, but this is wrong, provided you're careful to wear them correctly.

(Added: Emily Neff Berlin says in the comments, "Also, please do not buy masks, unless you are in a high risk demographic. They will reduce your risk of exposure some. But they are in short supply and health care/public health institutions need them more than most individuals, as part of work that will ultimately benefit large numbers of people.")

If you don't have surgical masks, home-made masks or scarves can also be effective. This study shows that home-made masks (made from tea cloth) were less effective than surgical masks, but still useful.

(Added Mar. 28: This SSC post reviews the literature and concludes, "If the shortage ends, and wearing a mask is cost-free, I agree with the guidelines from China, Hong Kong, and Japan – consider wearing a mask in high-risk situations like subways or crowded buildings. Wearing masks will not make you invincible, and if you risk compensate even a little it might do more harm than good. Realistically you should be avoiding high-risk situations like subways and crowded buildings as much as you possibly can. But if you have to go in them, yes, most likely a mask will help.")

 

C. Don’t put coronavirus in your face.

From Patrick LaVictoire:

Like most respiratory diseases, coronavirus is transmitted in water droplets coughed or sneezed out by sick people. If the droplets dry out completely, the virus is destroyed.

They dry out in air pretty quickly- if you’re more than ten feet away, you’re unlikely to inhale them. But on surfaces including metal, glass, and plastic, they can persist for hours or even days. (That’s where the bleach wipes come in; clean your sink handles, especially, in case someone comes in with the virus and washes it off.)

The biggest danger, then [if you're avoiding social contact with others], is that you will touch a surface with coronaviruses on it, and then (before washing your hands thoroughly) touch your mouth, nose, or eyes. Once the virus is in one of those, you’re likely to get sick.

So the number one tip is to learn, now, to stop touching your face with your hands. If your eye itches, at least use your sleeve. Carry a handkerchief in case you need to wipe your nose or mouth. Etc.

I hear that surface transmission wasn't the primary way SARS spread, so I'm not sure how worth worrying about this is. A lot of people have noted that coronavirus can survive on surfaces up to 9 days in certain conditions (or even longer if it's cold), but Will Eden says: "This paper (https://www.journalofhospitalinfection.com/…/S0195-6701(20…/) is the source of the 9 day figure. However that’s the maximum length on any surface under ideal conditions. In some cases it only lasts hours. And it doesn’t establish whether any of that is infectious!" (Finan Adamson notes that it can last longer than 9 days if temperature is cold.)

Regardless, my other three main recommendations are: spend less time touching surfaces that a large number of other people touch; try to minimize how much you touch your eyes, nose, or mouth; and wash your hands more often, using full medical hand-washing protocol (https://jagermo.sabic.uberspace.de/…/20…/02/Clipboard021.jpg). (Mnemonic version: https://www.facebook.com/…/a.2144449099383…/214446503271484/.) Note that for COVID-19, hand sanitizer isn't a good replacement for hand-washing.

 

D. Have emergency supplies.

I would recommend stockpiling at least a month of non-perishable food. 2-3 months is even better. Err on the side of buying food that you like; idiosyncratic favorite foods are less likely to be sold out on Amazon right now, and it's important to make your self-quarantine pleasant so you're less likely to want to take unnecessary risks later.

From Event Horizon (https://docs.google.com/…/1Rn6WrTat0Cb6gfatWv-TcSBToh3…/edit): "Most dedicated disaster prep food is already sold out, but you could get a bunch of canned foods (e.g. beans, fish, vegetables, fruits) and dry foods (e.g. rice, pasta, dried fruit, peanut butter) that you like and can eat."

I would similarly stock up on other essential items, especially medications you need.

 

E. Print out copies of your health records.

From Event Horizon: "If hospital infrastructure is overwhelmed, you may not be able to access this information. The most important information to have on hand is your history of major health problems and surgeries, immunization records, and medications you are currently taking. Here is a template for such a health record: https://docs.google.com/…/1fCCTcwrULo5w4vnymhziCVdctM…/edit…"

 

F. Disinfect surfaces.

(Especially commonly touched surfaces like door handles and light switches.)

https://www.who.int/…/who-china-joint-mission-on-covid-19-f… notes "In China, human-to-human transmission of the COVID-19 virus is largely occurring in families [...] most clusters (78%-85%) have occurred in families." Divia Eden comments: "One of my takeaways was that delivery of packages was unlikely to be a major vector, in China anyway."

That said, packages may still be the main risk source for you if relying on packages for food; and the risk may rise in contexts where containment measures have failed and the virus is more widespread globally. So if it's not too much trouble for you, or if you're unusually at risk, it probably makes sense to sanitize packages too.

The easy version of this is letting packages sit in direct sunlight for a while before opening them. Heat and UV radiation are good for killing coronavirus.

Fortunately, the hard version is only slightly harder, since coronaviruses are easy to kill with a wide variety of cleaning agents. From https://en.wikipedia.org/wiki/Viral_envelope, discussing enveloped viruses in general: "The lipid bilayer envelope of these viruses is relatively sensitive to desiccation, heat, and detergents, therefore these viruses are easier to sterilize than non-enveloped viruses, have limited survival outside host environments, and typically transfer directly from host to host."

Good options for cleaning agents include 70% isopropyl alcohol (NOTE: higher or lower percentages may not work; added citation: https://blog.gotopac.com/…/why-is-70-isopropyl-alcohol-ip…/…) or the items on this (CDC-referenced) list: https://www.americanchemistry.com/Novel-Coronavirus-Fightin….

 

G. Buy copper tape from Amazon (https://smile.amazon.com/…/ref=ppx_yo_dt_b_search_asin_title). and use it to cover things you commonly touch, like your cell phone and door handles.

Solid copper doesn't kill viruses on contact, but it makes it hard for viruses to survive on a timescale of hours (https://www.lesswrong.com/…/coronavirus-justified-practical…).

Added Mar. 27: try to minimize wrinkles in the tape, so that taped surfaces remain easy to disinfect. Robert Miles suggests: "Tape should be cut to the right size, and you need a tool which is finger shaped, harder than a finger but softer than copper - wood or plastic is good, I use the rounded end of a swiss army knife. Running that along seams and small creases makes them mostly disappear". Be careful of papercuts.

 

H. Probably stop taking NSAIDs like ibuprofen.

NSAIDs are immunosuppressive, and there's some suggestive evidence that they might make cases worse.

https://mobile.twitter.com/samira_jei…/…/1238885284332408832 - "In Germany and France, ICU physicians have noticed that the common thread amongst young patients needing #COVIDー19 related ICU admission is that they had been using NSAIDS (Advil, Motrin, Aleve, Aspirin)." She cites https://www.archyde.com/against-covid-19-the-minister-of-h…/, and there's a plausible mechanism (https://www.thelancet.com/…/la…/PIIS2213-2600(20)30116-8.pdf), but obviously the causation might be going the other way and people might be seeing patterns where they don't exist.

The WHO (and some thoughtful lit reviewers like Elizabeth van Nostrand) are very skeptical that the 'NSAIDs are dangerous' thing will turn out to be true once properly studied (https://twitter.com/WHO/status/1240409217997189128). Others find it more plausible. I'm not sure how worried to be about NSAIDs, but I expect it to be easy for most people to switch from NSAIDs to acetaminophen and other drugs, so that's what I recommend.

 

I. Consume 2,000-6,000 IU of Vitamin D daily, in the morning.

"Since COVID usually kills via pneumonia, and insufficient vitamin D appears to be a surprisingly large risk factor in respiratory infection, it’s probably pretty important to keep vitamin D levels sufficient (which in most people means supplementing it specifically, esp if there’s any quarantine that affects food)." (https://www.lesswrong.com/…/coronavirus-justified-practical…)

 

J. Run an air purifier.

By Sarah Constantin: "In a retrospective study in Utah hospitals, high concentrations of particulate matter in the air were associated with slightly but significantly higher (OR = 1.004) rates of admission to the emergency room for pneumonia, and slightly (OR = 1.02) but significantly higher rates of pneumonia mortality.[12] Having air filters in the home may be slightly protective."

Also, quit smoking (https://slatestarcodex.com/2020/03/27/coronalinks-3-27-20/).

 

K. Stay healthy: eat well, sleep well, get exercise.

 

 

 

3. Things to do if you get sick:

(Mar. 28 update: I largely rewrote this section today. This section remains relatively speculative and subject to change. COVID-19 is a new disease that we're still in the early stages of understanding, and as Sarah Constantin notes, there aren't many good studies on how best to treat flu- or pneumonia-like illnesses from home. Still, phlegm and flu wait for no man, and we're forced to make the best guesses we can with the available evidence.)

A. Prepare in advance.

Things to buy right now for if you get sick: Pedialyte or gatorade powder, over-the-counter inhalers, a humidifier, acetaminophen, mucinex/guaifenesin, pseudoephedrine, zinc lozenges, oral thermometers, and a finger pulse oximeter. Maybe hydroxychloroquine or chloroquine and/or a home oxygen concentrator, if you can find it online or get it prescribed by your doctor. See below for details.

While still healthy, take your temperature (orally) and use your finger pulse oximeter. Do this multiple times per day over several days, to make sure the devices are working and to get a sense of your baseline numbers.

Figure out who can help take care of you if you get sick.

 

B. Understand how COVID-19 usually presents and progresses, so you can make an informed guess about how likely you are to have it.

Direct testing can obviously help, but depending on where you are and what symptoms you have, it may be be very difficult to get tested in the US, and the test results may come back too late to be useful. It's still worth getting tested if circumstances allow, e.g., to clarify treatment priorities, aid in containment, or check for other infections. Per Sarah Constantin:

It’s important to get tested by a doctor if you have a respiratory illness you think is COVID-19. Even if you can’t get access to a COVID-19 test, you might also have a different bacterial or viral infection (either instead of or in addition to COVID-19) which is treatable by antivirals or antibiotics. It’s very common for viral pneumonia to be complicated by an opportunistic bacterial infection, and killing the bacteria can help improve outcomes.

As of Feb. 24, the WHO listed COVID-19 as causing these symptoms with the following frequencies (https://www.who.int/…/who-china-joint-mission-on-covid-19-f…):

fever (87.9%), dry cough (67.7%), fatigue (38.1%), sputum production (33.4%), shortness of breath (18.6%), sore throat (13.9%), headache (13.6%), myalgia [muscle pain] or arthralgia [joint pain] (14.8%), chills (11.4%), nausea or vomiting (5.0%), nasal congestion (4.8%), diarrhea (3.7%), and hemoptysis [coughing up blood] (0.9%), and conjunctival congestion [inflammation in the white of the eye] (0.8%).

(Also, up to 50% of infections might be asymptomatic, while still being contagious)

The WHO report continues:

People with COVID-19 generally develop signs and symptoms, including mild respiratory symptoms and fever, on an average of 5-6 days after infection. [...] Using available preliminary data, the median time from onset to clinical recovery for mild cases is approximately 2 weeks and is 3-6 weeks for patients with severe or critical disease. Preliminary data suggests that the time period from onset to the development of severe disease, including hypoxia [serious lack of oxygen], is 1 week.

From https://www.vox.com/…/coronavirus-symptoms-covid-19-sars-co…:

Covid-19 disease usually begins with mild fever, dry cough, sore throat and malaise,' writes Megan Murray, a professor of epidemiology at Harvard Medical School, in an FAQ for the Abundance Foundation. 'Unlike the coronavirus infections that cause the common cold, it is not usually associated with a runny nose.' These symptoms emerge five or six days after infection on average, but can show up in as little as a day or as much as two weeks after exposure.

From Business Insider, a day-by-day progression of typical cases:

Day 1: Patients run a fever. They may also experience fatigue, muscle pain, and a dry cough. A small minority may have had diarrhea or nausea one to two days before.

Day 5: Patients may have difficulty breathing — especially if they are older or have a preexisting health condition.

Day 7: This is how long it takes, on average, before patients are admitted to a hospital, according to the Wuhan University study.

Day 8: At this point, patients with severe cases (15%, according to the Chinese CDC) develop acute respiratory distress syndrome, an illness that occurs when fluid builds up the lungs. ARDS is often fatal.

Day 10: If patients have worsening symptoms, this is the time in the disease's progression when they're most likely to be admitted to the ICU. These patients probably have more abdominal pain and appetite loss than patients with milder cases. Only a small fraction

die: The current fatality rate hovers at about 2%.

Day 17: On average, people who recover from the virus are discharged from the hospital after 2 1/2 weeks.

Elizabeth van Nostrand has been looking into what the earliest symptoms of COVID-19 infection tend to be. She writes:

Most academic/medical papers start with the person’s first contact with the medical system, which is too late, so I looked at social media and news reports. These are obviously going to be biased towards people with symptoms severe enough to be interesting, but not so severe as to die. I also restricted myself to test-confirmed cases, which because I was also looking at mostly American sources biases things towards severe cases. And I’m counting on people to represent themselves honestly. So there’s a lot going against this sample.

In total I found 11 cases, plus two notes from doctors doing front line work. [...] From this very small and biased sample:

  • 36% of people started with a cough on their first day (55% if you count two people who had very mild symptoms on day 1 and developed a cough on day 2)
  • 64% started with a fever.
  • 18% of people started with both on the same day.
  • 18% started with neither symptom (but developed a cough on day 2)
  • 78% eventually developed a cough
  • 91% eventually developed a fever. The only person who didn’t eventually develop a fever I think might be a false positive, because his symptoms were very weird.
  • 27% had digestive symptoms (mostly nausea)
  • 1/3 of recovered people had been hospitalized. [...]

You may have heard that 80% of cases are mild. Keep in mind that that paper defined mild to include mild pneumonia, which I would classify as at least moderately severe.

From https://news.sky.com/…/coronavirus-experts-say-new-symptoms…:

The British Association of Otorhinolaryngology (ENT UK) say asymptomatic patients - ones who do not have a fever or a cough - could show a loss of smell or taste as symptoms after contracting coronavirus. [...] 'In [many] young patients, they do not have any significant symptoms such as the cough and fever, but they may have just the loss of sense of smell and taste, which suggests that these viruses are lodging in the nose.' [...] Dr Nathalie MacDermott, clinical lecturer at King's College London said infections that normally occur through the 'nose or the back of the throat" often lead to a loss in sense of smell and taste, but cautioned that research around the new symptoms for COVID-19 isn't yet widespread in the medical community.'

https://www.statnews.com/…/coronavirus-sense-of-smell-anos…/ reports that anywhere from 30% to 67% of COVID-19 patients temporarily lose their sense of smell.

Anecdotally, one of the handful of people I know who likely has COVID-19 (has the relevant symptoms, and is living with someone who tested positive) reports: "given the symptoms I'm seeing, it's a perfect match. Including the on and off nature of it, the chest pains, the shortness of breath, the loss of smell. (I just tried smelling a bottle of rubbing alcohol... smells like nothing! I'm having trouble telling whether my clothes need to be laundered.)" On Mar. 27 I decided to ask five other friends with plausible (but unconfirmed) COVID-19 cases about this; one other said they had extremely diminished sense of smell/taste, two said they did not, and two weren't sure.

One study found higher rates of digestive issues (103 out of 204 cases), broadly construed. In https://www.medicalnewstoday.com/…/covid-19-digestive-sympt…, 40% of patients experienced lack of appetite, 17% diarrhea, 2% vomiting, 1% abdominal pain. "Moreover, the digestive symptoms among the larger group grew more severe as the severity of COVID-19 increased[.]"

COVID-19 can also present with rashes on the limbs: https://www.ncbi.nlm.nih.gov/pubmed/32190904. And the virus can apparently infiltrate cerebrospinal fluid and cause neurological symptoms: https://srconstantin.github.io/…/COVID-19-young-people-risk….

So... apparently COVID-19 symptoms include "approximately everything".

COVID-19's presentation seems to vary a lot. Typically, if you see symptoms at all, you'll see respiratory symptoms such as coughing, chest tightness, or shortness of breath; and these are the symptoms to keep the closest eye on, since COVID-19 deaths are usually via respiratory failure. But I've also heard accounts of pretty debilitating-sounding fatigue or intense/long-lasting fever. E.g. (from an unconfirmed case, http://freakytrigger.co.uk/…/things-i-wish-id-known-before…/):

[...] IT CAN LAST FOR AGES: Onto what I didn’t expect (or hadn’t been prepared for) symptoms wise. The main thing was the sheer length of it – though again, in my own case it was over very rapidly. Isabel wasn’t so lucky. Fevers are nasty, but this was a fever that ground on for days without really breaking or spiking. The duration of C19 seems to be one of the unusual things about it – in Isabel’s case it peaked around day 8 (the worst of the fever), then again on day 10 (the worst of the breathing issues, which luckily were still mild). Apparently for hospitalised survivors in Wuhan the median release day was Day 24. Be prepared for a long haul.

IT EBBS AND FLOWS: This is something I really wish I’d been expecting – for Isabel, C19 didn’t follow a predictable pattern of worsening, peaking and recovery. There was a period of initial but manageable illness, then a rapid decline into being entirely bedridden, then two separate peaks of illness with improvements in between, and only now a sustained recovery. It took her until Day 11 to say “I’m feeling a bit better”, and as an observer there were clear rallies and declines along the way, which made everything particularly nerve-racking: you never quite know if things have improved, and declines are especially frightening.

THE BEST-KNOWN SYMPTOMS MIGHT NOT BE THE WORST: If you’re like me, when you think of Coronavirus you think fever, dry cough and changes in breathing, which are the signature symptoms. Isabel had all of those, but for her the worst effects were exhaustion, nausea, aches and dehydration. She was weakened by it to a degree I’ve never seen outside very old and ailing relatives, well beyond any flu either of us have had. She needed a constant supply of painkillers and water (which she was often too weak to actually lift to her lips) and had zero appetite. In a non-pandemic – or if she was on her own – she would definitely have been in hospital. As it was, fortunately her breathing was never bad enough to need that."

The "ebbs and flows" aspect of COVID-19 seems very common. E.g., from another unconfirmed case:

3/7 - I attended a party with at least one known person that tested positive, and >5 others that reported similar symptoms on an almost identical timeline

3/9 - Day 1 - Mild fever (99.5) for a few hours. Chills. Headache. It was gone by the evening

3/10-11 - Days 2-3 - Muscle pain, fatigue - both pretty mild

3/12-14 - Days 4-6 - I felt better, no symptoms at all. This led me to believe it was just a head cold

3/15-16 - Days 7-8 - I had a tightness in my chest and some difficulty breathing. This is when I started suspecting it might not be a cold

3/17 - Day 9 - Cough started. Mild, but dry. Throat is irritated.

3/18 - Day 10 - No more cough, no more chest tightness, no trouble breathing. Throat is slightly irritated but feels like I’m getting better

3/19-20 - Days 11-12 - Uh oh. Fever comes and goes throughout the day, much harder to breath, cough is back and is worse. The shortness of breath was sudden and very unpleasant.

3/21 - Day 13 - Today. Right now I feel better than I did all week. No fever, no difficulty breathing, and no cough. But I’ve been tricked before so I’m being patient and giving it a few more days to be sure. I don’t think I’m quite out of the woods yet. [...]

Well, it definitely wasn't over when I wrote this post on day 13. That night had another wave of chest pain and shortness of breath and days 14 and 15 felt like a low grade asthma attack that wouldn't go away.

Days 16 and 17 - The dry cough turned into a productive cough and the combination of mucinex and hot tea gave me some relief.

Today, day 18, I finally feel mostly ok. I'm not coughing and I can breathe!

Unfortunately, the lab I got tested with was shut down by the FDA so I won't be getting my test result: https://www.nytimes.com/…/coronavirus-home-testing-swab-kit… [...]

Some notes:

1. Don’t trust the 'lull'. This progression seems to be pretty common - one slightly feverish day, then back to normal, and then the second wave. Or third [and fourth], in my case. I wish I had been more aware of this - I exposed some people on days 4-6. So far none of them are showing symptoms, but I would have acted differently if I had known this was a typical covid pattern.

2. It is really useful to have a pulse oximeter. Get one on amazon for <20$. This let me check my vitals even in the middle of the worst part of not being able to breathe and see that my oxygen levels were normal (97-99). I would've made my way to a hospital if it had dropped <90[.]

Symptoms like runny noses are useful to track because their presence provides some evidence that you don't have COVID-19. Colds tend to cause sneezing, whereas COVID-19 and flu don't cause sneezing. Colds also cause runny or stuffy nose, which are rare in COVID-19 (and somewhat uncommon in the flu). And the flu has a sudden onset, whereas COVID-19 and colds usually have gradual onsets.

That said, since COVID-19 is especially dangerous and can present in a variety of ways (and it's always possible you have COVID-19 and another illness), you should be careful not to prematurely rule out the possibility that you have COVID-19.

 

C. Take zinc immediately if you start feeling any cold-, flu-, or COVID-19-like symptoms.

From virologist James Robb

Zinc lozenges "have been proven to be effective in blocking coronavirus (and most other viruses) from multiplying in your throat and nasopharynx. Use as directed several times each day when you begin to feel ANY "cold-like" symptoms beginning. It is best to lie down and let the lozenge dissolve in the back of your throat and nasopharynx. Cold-Eeze lozenges is one brand available, but there are other brands available." (Sources: this + this)

The discussion on LessWrong suggests that ordinary zinc lozenges may be ineffective for various reasons, and that one of the only products that seems likely to be effective is 'Life Extension Enhanced Zinc Lozenges' (which are currently sold out on Amazon).

One option that maybe makes sense is dripping a small amount of liquid ionic zinc down the back of your throat when you start feeling ill? I'm not sure. Be warned, however, that zinc nasal sprays have been found to permanently remove people's sense of smell, and regular use of zinc in other forms may also damage your sense of taste or smell over time.

From LessWrong's question "What should we do once infected?":

Take zinc at the first symptom. [...] The method of action is zinc ions attaching to your throat. So pills are useless. It has to be a lozenge. [...] Chris Masterjohn claims only zinc-gluconate and -acetate work. I don't know if this is true, but the only studies I found used gluconate and acetate, so it seems wise to prefer them. [...] The terrible taste and loss of sense of smell says it’s working, unless you already lost your sense of smell to COVID.

 

D. Start monitoring your oxygen immediately if you develop a fever or experience significant chest tightness or difficulty breathing.

From residents of the Event Horizon house:

Since COVID-19 is a disease with significant respiratory involvement, and that's the pathway by which it usually kills, you'll want to go to the hospital if you’re having trouble breathing, and your blood oxygen levels are consistently below ~90-94% (for people at sea level), while you are using the pulse ox as directed. (Brief dips should generally not worry you, due to normal fluctuations and the imperfection of the measurement.)

(Also from Event Horizon: "[F]or adults, you’re generally considered to have a fever if you have an orally measured body temperature of 100.4°F / 38 °C).")

Eli Morningstar adds:

Advice to avoid freaking yourself out with a home pulse oximeter (avoid user error):

  • Keep your hand below your heart when measuring
  • Don't wear nail polish on the finger you're using
  • Hold something warm first, ie don't have cold hands

Some people are also buying home oxygen concentrators in case they experience serious symptoms while hospitals are overloaded. Connor Flexman discusses home use of both oximeters and concentrators here:

Tl;dr: Not knowing much about this, my current policy is to go to a hospital if PaO2 drops below ~92% and my hospital isn’t completely overrun, unless my PaO2 is naturally low or some other extenuating circumstance. If I was forced to use an oxygen concentrator outside of a hospital, I would target a ~~94-96% PaO2 range, trying very hard to make sure I didn’t hit 99%

If you do have COVID and shortness of breath, when do you go to a hospital?

Hopefully you already have a pulse oximeter as Julia Wise recommends. But sources say anywhere between 90 and 95% PaO2 is the threshold for hospitalization (WHO says <= 93% is classified as severe, ctrl+f “O2”), while other sources say you should threshold on trouble breathing and shortness of breath, not the actual PaO2 number.

It seems to me that using “trouble breathing” as the indicator would track the lung blockages and thus immune response relatively well, while O2 as an indicator would track the danger metric directly (if in fact the primary source of death is insufficient oxygen; if anyone knows this, would be useful).

The benefit of looking at trouble breathing is that it’s an advance indicator. Usually people progress from oxygen therapy to ventilators relatively quickly. If you have naturally low PaO2, your O2 might drop under threshold (say, 93%) in the early stages with mild trouble breathing, but you wouldn’t have much of a dangerous immune response until later. In this case, you’d have wanted to use difficulty breathing as your indicator instead of PaO2.

That being said, having low oxygen seems pretty bad for you, both by common sense and science. For example, 92% or lower is associated with increased morbidity in pneumonia patients; <90% is increased with 36% increased morbidity. Since it’s hard to measure even moderate effects due to the treatment-correlated-with-severity issue, my guess is that there’s some general bodily harm from reduced oxygen even at levels like 95%, though I don’t know how much. So at some PaO2 threshold, I think you want to be supplementing oxygen even if your breathing doesn’t feel that difficult.

Unfortunately, it seems like you can’t supplement oxygen at 95%, because over-oxygenating causes neuronal damage. Standard targets appear to be 94-98% or 92-96%. This study says it seems bad to set your target range during oxygen therapy to greater than 92-96%, because one inevitably exceeds the upper target occasionally. This review/musing muses that it’s a difficult problem, evidence for hyperoxaemia being pretty bad is “comparatively strong”, but not strong enough to warrant especially conservative oxygen titration. Because of these numbers, I think 92-93% is a reasonable threshold to self-hospitalize, since anything above this means they probably shouldn’t be oxygenating you anyways.

If hospitals are overloaded and you have to do oxygen therapy yourself (really try not to do this), I think the targets above are still reasonable, subject to your ability to titrate well with the machine. If you have lots of trouble, of course be conservative. However, you may be able to do better than hospitals: the first study above says that “even in a research setting in the intensive care unit, in which patients receiving mechanical ventilation are closely monitored, most patients who were randomized to an SpO2 target of 90–92% and were receiving supplementary oxygen did not have their inspired oxygen reduced if the SpO2 was 99% or 100%.” So—seems like you could easily do better monitoring than this if you were oxygenating at home. This is why I would probably shoot for 94-96% myself.

If hospitals are overloaded and you have to do oxygen therapy yourself (really try not to do this), I think the targets above are still reasonable, subject to your ability to titrate well with the machine. If you have lots of trouble, of course be conservative. However, you may be able to do better than hospitals: the first study above says that 'even in a research setting in the intensive care unit, in which patients receiving mechanical ventilation are closely monitored, most patients who were randomized to an SpO2 target of 90–92% and were receiving supplementary oxygen did not have their inspired oxygen reduced if the SpO2 was 99% or 100%.' So—seems like you could easily do better monitoring than this if you were oxygenating at home. This is why I would probably shoot for 94-96% myself.

I want to emphasize that you may need to go to the hospital on very short notice. Serious COVID-19 cases appear to not-infrequently progress from 'little or no care needed' to 'serious oxygen therapy needed immediately' on very short timescales. E.g., from https://www.propublica.org/…/a-medical-worker-describes--te…:

I have patients in their early 40s and, yeah, I was kind of shocked. I’m seeing people who look relatively healthy with a minimal health history, and they are completely wiped out, like they’ve been hit by a truck. This is knocking out what should be perfectly fit, healthy people. Patients will be on minimal support, on a little bit of oxygen, and then all of a sudden, they go into complete respiratory arrest, shut down and can’t breathe at all.

The second week of symptom presentation seems like it may be particularly dangerous. Please monitor symptoms carefully, even if your symptoms were relatively mild in the first week. From https://www.cdc.gov/…/clinical-guidance-management-patients…:

Some reports suggest the potential for clinical deterioration during the second week of illness. In one report, among patients with confirmed COVID-19 and pneumonia, just over half of patients developed dyspnea [labored breathing] a median of 8 days after illness onset (range: 5–13 days). In another report, the mean time from illness onset to hospital admission with pneumonia was 9 days. Acute respiratory distress syndrome (ARDS) developed in 17–29% of hospitalized patients, and secondary infection developed in 10%. In one report, the median time from symptom onset to ARDS was 8 days.

Depending on how serious your symptoms are, and on how crowded nearby hospitals are at the time, you may want to go to the hospital even if your breathing is OK. If possible, talk to a doctor over the phone/video to get their recommendations. The above is meant to be advice about when you definitely should receive hospital-level care; but it's not necessarily smart to wait until the last moment.

All that said, for several reasons, it's very often* a bad idea to go to a hospital during a pandemic when it isn't absolutely necessary:

  • You might not have COVID-19. Going to a hospital may then expose you to COVID-19, on top of your other illness. (Catching COVID-19 is much more dangerous for people who have another illness.)
  • You might have COVID-19 and end up exposed to a lot more copies of the virus early in your disease progression, which is likely to seriously worsen your symptoms. Discussion of the importance of viral load here: https://www.facebook.com/robert.wiblin/posts/887350766835. But Nick Tarleton says: "[I] would naively imagine that once someone is solidly {infected + mounting an immune response}, more external viral load would be a pretty small factor."
  • Hospitals can provide superior care for very severe cases -- and they have the crucial advantage of being able to care *at all* for patients who require mechanical ventilation. But for more mild symptom management, an overtaxed hospital may provide worse care than you could receive at home, since medical staff's limited attention needs to mostly go to patients with the most serious cases.

Similar advice from Elizabeth van Nostrand: https://www.lesswrong.com/…/what-should-we-do-once-infected…

I suggest monitoring how busy the hospitals nearest to you seem to be as the pandemic progresses, and calling ahead if possible to get advice and information about the availability of ICU beds, etc.

In a shortage, also check whether your local hospital knows that they can split ventilator tubes (and double the air flow) to double their effective number of ventilators (https://thehill.com/…/489817-new-york-hospital-ready-to-spl…). Ventilator splitters can be 3D printed easily if the hospital doesn't have any on hand.

 

E. Take care of yourself.

From Duncan Sabien:

Symptom mitigation seems extremely likely to be extremely important, especially those related to the respiratory tract. Early prophylactic measures (zinc lozenges, things to soothe throat and prevent coughing), Tylenol (NOT NSAIDs). Lots of fluids with lots of electrolytes (Pedialyte if you can get it, Gatorade if you can't). Temperature regulation.

The biggest thing I'm worried about is permanent post-recovery respiratory problems, and it seems to me that most of those are caused by symptomatic damage rather than by the direct actions of the virus itself.

I believe that most (though not all!) sources these days suspect that fevers are good by default, and you shouldn't try to lower your fever unless it gets dangerously high. Regarding what counts as "dangerously high", Elizabeth van Nostrand says: "I was taught 103ºF, some people say 104ºF, that’s probably the range."

From Event Horizon:

[If] your fever is dangerously high (103°F / 39.4°C or higher) [then you may need to] lower your body temperature manually. Ways to treat fever safely: acetaminophen/paracetamol (do not exceed recommended dose; do NOT use NSAIDs); Drinking more fluids; Take a bath (but NOT an ice bath or a cold bath); Place cool washcloths (NOT icepacks) under the armpits and in the groin area.

[...] Have something to help you rehydrate if you are sick and losing fluids. Gatorade Powder (https://smile.amazon.com/Gatorade-Thirst-Quencher-Powder…/…/) is a good option because you can buy it in bulk, unlike Pedialyte. Also, liking the things that you drink might ensure you keep doing it. Here (https://med.virginia.edu/…/Homemade-Oral-Rehydration-Soluti…) is a guide to creating oral rehydration solution (used to treat fatal diarrhea, also useful for vomiting and general dehydration) from a variety of bases and household ingredients."

From Divia Eden: "I would get mucinex and a humidifier if possible." See the nurse recommendations here. Elizabeth van Nostrand says: "Take pseudoephedrine if you have unpleasant sinus pressure." (Note: not phenylephrine / Sudafed PE, which is apparently useless)

Stay warm, take it easy, and get lots of rest.

 

F. Consider taking more extreme measures if you're experiencing serious COVID-19 symptoms, or if you're at-risk (i.e., you're older or have other health issues) or have the resources to take bonus precautions.

As noted above, moderate-to-severe cases may benefit from a home oxygen concentrator. Oxygen concentrators have been used in a much larger number of COVID-19 cases to date than mechanical ventilators, and unlike ventilators, are easy to operate.

If your case is severe but there aren't hospital beds available, postural drainage strikes me as something that *might* possibly help.

Speculative and risky, but: If you can, you may want to acquire chloroquine or hydroxychloroquine. Be sure to read the entire write-up at https://docs.google.com/…/160RKDODAa-MTORfAqbuc25V8WDkLjqj…/.

Specifically for people in high-risk groups, Anjali Gopal suggests: "can you sign [...] up for clinical trials for antiviral drugs in nearby research hospitals? Some research coming out around this has started to show efficacy of remdesivir, chloroquine, and hydroxychloroquine wrt covid, though of course, this is still all very speculative and needs to be verified by RCTs. (A lot of these trials are often only open for people in high risk groups[.)]" Elizabeth van Nostrand: "One place I have found to find RCTs is https://clinicaltrials.gov/ . Normally I would verify the details of how to join but I assume they are busy right now."



Discuss

Coronavirus Virology: A Beginner’s Guide

28 марта, 2020 - 23:47
Published on March 28, 2020 8:47 PM GMT

Introduction

This is aimed at those interested in a biological understanding of the basic features of a coronavirus, but who do not have a biological/chemical background to speak of—if you haven’t done biology or chemistry since high school, this should be for you. It starts at square one and it oversimplifies many things. That said, I hope it is at least clear, and allows you to read scientific papers on the features of SARS-CoV-2 (novel coronavirus) without getting too much of a headache.

Viruses mostly just use their host’s (that’s you) metabolism to make more viruses. To understand how that occurs, we will begin with some basic (host) cell physiology—how DNA, RNA, and proteins relate to one another, and what a lipid bilayer is—before moving on to look at the anatomy of a coronavirus, and then finally a handful of specific features that make SARS-CoV-2 so dangerous.

DISCLAIMER: There should be nothing controversial or disputed here, and I have specifically avoided giving information that is contested. This is not least because I am a medical student, not a virologist or epidemiologist. The aim of this guide is just to introduce the basic science, nothing more.

Many thanks to Jaden Kimura for comments and proof-reading.

How does a cell work, anyway?

In your own cells, DNA codes for all of the proteins you produce, which determines how you build cells and, eventually, a body. Think of it as the source code. Short stretches of it are ‘compiled’ (transcribed) onto RNA, which is a very similar but less stable molecule. Only RNA can be actually ‘run’ by translating it into functional proteins.

DNA is double-stranded, but the two strands are not the same—they’re kind of chemical mirror images of one another. One is ‘positive sense’ and the other ‘negative sense’. Because of the way that they mirror one another, they bind tightly together. When new RNA is made, it is ‘copied’, through a similar binding, from the negative sense strand—it looks just like the positive sense strand. This means that your protein-making machinery (ribosomes) is all used to reading positive sense RNA.

The outside ‘wall’ of a cell is made of a lipid bilayer. The bilayer is made up of molecules with a small polar ‘head’ and a long non-polar tail. Because water is very polar (the electrons are clustered near the oxygen nucleus, making the hydrogens slightly positively charged), the polar ‘head’ can form very stable relationships with water—it is ‘hydrophilic’. As the opposite is true of the very non-polar part of the molecule (lipophilic/hydrophobic tail), the molecules arrange themselves to stable states where the tails are touching one another, and the heads are touching the water—a bilayered sphere. Into this bilayer, different proteins can be ‘inserted’ if they have a non-polar section (or sections) and polar regions such that they stably localise inside or through the lipid bilayer.

How does a coronavirus work?

Coronaviruses are positive sense, RNA, enveloped viruses. Hopefully you recognise some of those terms, but we’ll just highlight the consequences of this particular structure.

The genetic material in a coronavirus consists only of positive sense RNA. It can therefore be shoved directly into your ribosomes to produce coronavirus proteins, without ever having to be modified by enzymes. This means that coronavirus RNA on its own is theoretically infectious—if you injected it into human cells, it would use your ribosomes to assemble new virus particles.

In some viruses, the genetic material is basically the entire virus, packaged into some proteins (a nucleocapsid). Coronaviruses, however, also have an external envelope surrounding them. This envelope is made up of host cell membrane—a fatty lipid bilayer, just like your own cells, but with a couple of viral proteins inserted into it.

Because the bilayer relies on the polar/non-polar relations to remain stable, molecules that are similarly structured-- with a polar and non-polar area (amphiphilic molecules) -- can disrupt the stability of this arrangement at sufficiently high concentrations. They insert into the membrane and pull the lipids apart into much smaller, now more stable, arrangements. Without a lipid bilayer, the viral particle cannot insert itself into cells effectively, and is inactive. Alcohol and soap are precisely such molecules, which is why they are so effective against coronaviruses.

The final feature worth noting about the coronavirus is the spike protein. This is a protein which binds to a host protein (on the cell surface) and causes the envelope to fuse with the cell surface membrane, releasing the nucleocapsid into the cytoplasm (the inside of the cell). Because different species, and different cell lines in a given species, express different cell surface proteins, this leads to the majority of both species specificity and ‘type-of-infection’ specificity—only some viruses are capable of causing respiratory infections, to take a completely random example.

Why is SARS-CoV-2 so dangerous?

There are essentially only two things that make a virus dangerous: how infectious it is, and how serious it is once you have it. The first is roughly described by the R0 (basic reproduction rate), and the second by the case fatality rate.

The first major point is just how bluntly infectious SARS-CoV-2 is. The R0 is a measure of, on average, how many people an infected person will go on to infect (in a population where immunity is negligible). Seasonal flu has an R0 of ~1.5 – each person infects, on average, 1-2 further people. MERS’ R0 was just ~0.7—less than one person was infected per person, meaning it isn’t really capable of spreading among humans. Current estimates of SARS-CoV-2 R0 vary a lot, but it looks like it’s between 3 and 5. Exponential growth means that the difference between 1.5 and 3 is phenomenal—over only 5 ‘generations’, a virus with an R0 of 3 will have infected ~245 people; a virus with R0=1.5 only ~8.

However, this clearly isn’t the whole story—SARS had a similar R0, and only infected around 8,000 people worldwide. Why? SARS cannot be transmitted from people who are asymptomatic. This means that isolation of people with symptoms is highly effective—following containment measures, the effective R0 is thought to have dropped to around 0.4. However, as has been discussed already on LW, this doesn't seem to be true of SARS-CoV-2. Firstly, it seems that people are infectious for as much as 48 hours in advance of any symptoms. Secondly, it’s likely (though, for obvious reasons, hard to prove) that a significant proportion of COVID-19 cases are either totally or mostly asymptomatic, particularly in children. Combined with a relatively long incubation period (averaging 5 days but likely up to 13 or 14 in the young), this means that by the time cases are presenting to hospitals in large numbers, the disease is already running rampant in the general population.

The other half of the equation—severity of disease—is fairly self-evident, not to mention well-discussed. Current estimates of the case fatality rate (the proportion of people who die of COVID-19, given that they have the disease) are around 2-3%. This is much lower than, for instance, SARS—11%, as well as a number of other diseases in humans (TB; 43%, tetanus 50%, Ebola 83%). The real problem is, of course, that these diseases are much less infectious. Not only do they affect fewer people, but they affect fewer people at one time. Much higher numbers of people will require critical care beds and ventilators, which will not be available through the peak of the epidemic. This seems set to push the deaths into the millions over the coming months, particularly in poorer countries.


Further Resources/Bibliography

A talk with more in depth discussion of previous epidemics and SARS-CoV-2 (excellent not least because it's free)

Mims' Medical Microbiology (Chapter one in particular is likely to be useful if you can find a PDF)

Principles of Virology (an excellent textbook if you're looking to go further; useful throughout for this topic)

Biocalculus-- Stewart and Day (probably the least useful listed here)



Discuss

Programming: Cascading Failure chains

28 марта, 2020 - 22:22
Published on March 28, 2020 7:22 PM GMT

The concept of a cascading failure chain can be demonstrated by this block of python. Don't worry if you don't know python, I'll try to explain it.

.mjx-chtml {display: inline-block; line-height: 0; text-indent: 0; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 100%; font-size-adjust: none; letter-spacing: normal; word-wrap: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0; min-height: 0; border: 0; margin: 0; padding: 1px 0} .MJXc-display {display: block; text-align: center; margin: 1em 0; padding: 0} .mjx-chtml[tabindex]:focus, body :focus .mjx-chtml[tabindex] {display: inline-table} .mjx-full-width {text-align: center; display: table-cell!important; width: 10000em} .mjx-math {display: inline-block; border-collapse: separate; border-spacing: 0} .mjx-math * {display: inline-block; -webkit-box-sizing: content-box!important; -moz-box-sizing: content-box!important; box-sizing: content-box!important; text-align: left} .mjx-numerator {display: block; text-align: center} .mjx-denominator {display: block; text-align: center} .MJXc-stacked {height: 0; position: relative} .MJXc-stacked > * {position: absolute} .MJXc-bevelled > * {display: inline-block} .mjx-stack {display: inline-block} .mjx-op {display: block} .mjx-under {display: table-cell} .mjx-over {display: block} .mjx-over > * {padding-left: 0px!important; padding-right: 0px!important} .mjx-under > * {padding-left: 0px!important; padding-right: 0px!important} .mjx-stack > .mjx-sup {display: block} .mjx-stack > .mjx-sub {display: block} .mjx-prestack > .mjx-presup {display: block} .mjx-prestack > .mjx-presub {display: block} .mjx-delim-h > .mjx-char {display: inline-block} .mjx-surd {vertical-align: top} .mjx-mphantom * {visibility: hidden} .mjx-merror {background-color: #FFFF88; color: #CC0000; border: 1px solid #CC0000; padding: 2px 3px; font-style: normal; font-size: 90%} .mjx-annotation-xml {line-height: normal} .mjx-menclose > svg {fill: none; stroke: currentColor} .mjx-mtr {display: table-row} .mjx-mlabeledtr {display: table-row} .mjx-mtd {display: table-cell; text-align: center} .mjx-label {display: table-row} .mjx-box {display: inline-block} .mjx-block {display: block} .mjx-span {display: inline} .mjx-char {display: block; white-space: pre} .mjx-itable {display: inline-table; width: auto} .mjx-row {display: table-row} .mjx-cell {display: table-cell} .mjx-table {display: table; width: 100%} .mjx-line {display: block; height: 0} .mjx-strut {width: 0; padding-top: 1em} .mjx-vsize {width: 0} .MJXc-space1 {margin-left: .167em} .MJXc-space2 {margin-left: .222em} .MJXc-space3 {margin-left: .278em} .mjx-test.mjx-test-display {display: table!important} .mjx-test.mjx-test-inline {display: inline!important; margin-right: -1px} .mjx-test.mjx-test-default {display: block!important; clear: both} .mjx-ex-box {display: inline-block!important; position: absolute; overflow: hidden; min-height: 0; max-height: none; padding: 0; border: 0; margin: 0; width: 1px; height: 60ex} .mjx-test-inline .mjx-left-box {display: inline-block; width: 0; float: left} .mjx-test-inline .mjx-right-box {display: inline-block; width: 0; float: right} .mjx-test-display .mjx-right-box {display: table-cell!important; width: 10000em!important; min-width: 0; max-width: none; padding: 0; border: 0; margin: 0} .MJXc-TeX-unknown-R {font-family: monospace; font-style: normal; font-weight: normal} .MJXc-TeX-unknown-I {font-family: monospace; font-style: italic; font-weight: normal} .MJXc-TeX-unknown-B {font-family: monospace; font-style: normal; font-weight: bold} .MJXc-TeX-unknown-BI {font-family: monospace; font-style: italic; font-weight: bold} .MJXc-TeX-ams-R {font-family: MJXc-TeX-ams-R,MJXc-TeX-ams-Rw} .MJXc-TeX-cal-B {font-family: MJXc-TeX-cal-B,MJXc-TeX-cal-Bx,MJXc-TeX-cal-Bw} .MJXc-TeX-frak-R {font-family: MJXc-TeX-frak-R,MJXc-TeX-frak-Rw} .MJXc-TeX-frak-B {font-family: MJXc-TeX-frak-B,MJXc-TeX-frak-Bx,MJXc-TeX-frak-Bw} .MJXc-TeX-math-BI {font-family: MJXc-TeX-math-BI,MJXc-TeX-math-BIx,MJXc-TeX-math-BIw} .MJXc-TeX-sans-R {font-family: MJXc-TeX-sans-R,MJXc-TeX-sans-Rw} .MJXc-TeX-sans-B {font-family: MJXc-TeX-sans-B,MJXc-TeX-sans-Bx,MJXc-TeX-sans-Bw} .MJXc-TeX-sans-I {font-family: MJXc-TeX-sans-I,MJXc-TeX-sans-Ix,MJXc-TeX-sans-Iw} .MJXc-TeX-script-R {font-family: MJXc-TeX-script-R,MJXc-TeX-script-Rw} .MJXc-TeX-type-R {font-family: MJXc-TeX-type-R,MJXc-TeX-type-Rw} .MJXc-TeX-cal-R {font-family: MJXc-TeX-cal-R,MJXc-TeX-cal-Rw} .MJXc-TeX-main-B {font-family: MJXc-TeX-main-B,MJXc-TeX-main-Bx,MJXc-TeX-main-Bw} .MJXc-TeX-main-I {font-family: MJXc-TeX-main-I,MJXc-TeX-main-Ix,MJXc-TeX-main-Iw} .MJXc-TeX-main-R {font-family: MJXc-TeX-main-R,MJXc-TeX-main-Rw} .MJXc-TeX-math-I {font-family: MJXc-TeX-math-I,MJXc-TeX-math-Ix,MJXc-TeX-math-Iw} .MJXc-TeX-size1-R {font-family: MJXc-TeX-size1-R,MJXc-TeX-size1-Rw} .MJXc-TeX-size2-R {font-family: MJXc-TeX-size2-R,MJXc-TeX-size2-Rw} .MJXc-TeX-size3-R {font-family: MJXc-TeX-size3-R,MJXc-TeX-size3-Rw} .MJXc-TeX-size4-R {font-family: MJXc-TeX-size4-R,MJXc-TeX-size4-Rw} .MJXc-TeX-vec-R {font-family: MJXc-TeX-vec-R,MJXc-TeX-vec-Rw} .MJXc-TeX-vec-B {font-family: MJXc-TeX-vec-B,MJXc-TeX-vec-Bx,MJXc-TeX-vec-Bw} @font-face {font-family: MJXc-TeX-ams-R; 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src: local('MathJax_Fraktur'), local('MathJax_Fraktur-Regular')} @font-face {font-family: MJXc-TeX-frak-Rw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Fraktur-Regular.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Fraktur-Regular.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Fraktur-Regular.otf') format('opentype')} @font-face {font-family: MJXc-TeX-frak-B; src: local('MathJax_Fraktur Bold'), local('MathJax_Fraktur-Bold')} @font-face {font-family: MJXc-TeX-frak-Bx; src: local('MathJax_Fraktur'); font-weight: bold} @font-face {font-family: MJXc-TeX-frak-Bw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Fraktur-Bold.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Fraktur-Bold.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Fraktur-Bold.otf') format('opentype')} @font-face {font-family: MJXc-TeX-math-BI; src: local('MathJax_Math BoldItalic'), local('MathJax_Math-BoldItalic')} @font-face {font-family: MJXc-TeX-math-BIx; src: local('MathJax_Math'); font-weight: bold; font-style: italic} @font-face {font-family: MJXc-TeX-math-BIw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Math-BoldItalic.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Math-BoldItalic.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Math-BoldItalic.otf') format('opentype')} @font-face {font-family: MJXc-TeX-sans-R; src: local('MathJax_SansSerif'), local('MathJax_SansSerif-Regular')} @font-face {font-family: MJXc-TeX-sans-Rw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_SansSerif-Regular.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_SansSerif-Regular.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_SansSerif-Regular.otf') format('opentype')} @font-face {font-family: MJXc-TeX-sans-B; src: local('MathJax_SansSerif Bold'), local('MathJax_SansSerif-Bold')} @font-face {font-family: MJXc-TeX-sans-Bx; src: local('MathJax_SansSerif'); font-weight: bold} @font-face {font-family: MJXc-TeX-sans-Bw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_SansSerif-Bold.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_SansSerif-Bold.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_SansSerif-Bold.otf') format('opentype')} @font-face {font-family: MJXc-TeX-sans-I; src: local('MathJax_SansSerif Italic'), local('MathJax_SansSerif-Italic')} @font-face {font-family: MJXc-TeX-sans-Ix; src: local('MathJax_SansSerif'); font-style: italic} @font-face {font-family: MJXc-TeX-sans-Iw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_SansSerif-Italic.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_SansSerif-Italic.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_SansSerif-Italic.otf') format('opentype')} @font-face {font-family: MJXc-TeX-script-R; src: local('MathJax_Script'), local('MathJax_Script-Regular')} @font-face {font-family: MJXc-TeX-script-Rw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Script-Regular.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Script-Regular.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Script-Regular.otf') format('opentype')} @font-face {font-family: MJXc-TeX-type-R; src: local('MathJax_Typewriter'), local('MathJax_Typewriter-Regular')} @font-face {font-family: MJXc-TeX-type-Rw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Typewriter-Regular.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Typewriter-Regular.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Typewriter-Regular.otf') format('opentype')} @font-face {font-family: MJXc-TeX-cal-R; src: local('MathJax_Caligraphic'), local('MathJax_Caligraphic-Regular')} @font-face {font-family: MJXc-TeX-cal-Rw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Caligraphic-Regular.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Caligraphic-Regular.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Caligraphic-Regular.otf') format('opentype')} @font-face {font-family: MJXc-TeX-main-B; src: local('MathJax_Main Bold'), local('MathJax_Main-Bold')} @font-face {font-family: MJXc-TeX-main-Bx; src: local('MathJax_Main'); font-weight: bold} @font-face {font-family: MJXc-TeX-main-Bw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Main-Bold.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Main-Bold.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Main-Bold.otf') format('opentype')} @font-face {font-family: MJXc-TeX-main-I; src: local('MathJax_Main Italic'), local('MathJax_Main-Italic')} @font-face {font-family: MJXc-TeX-main-Ix; src: local('MathJax_Main'); font-style: italic} @font-face {font-family: MJXc-TeX-main-Iw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Main-Italic.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Main-Italic.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Main-Italic.otf') format('opentype')} @font-face {font-family: MJXc-TeX-main-R; src: local('MathJax_Main'), local('MathJax_Main-Regular')} @font-face {font-family: MJXc-TeX-main-Rw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Main-Regular.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Main-Regular.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Main-Regular.otf') format('opentype')} @font-face {font-family: MJXc-TeX-math-I; src: local('MathJax_Math Italic'), local('MathJax_Math-Italic')} @font-face {font-family: MJXc-TeX-math-Ix; src: local('MathJax_Math'); font-style: italic} @font-face {font-family: MJXc-TeX-math-Iw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Math-Italic.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Math-Italic.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Math-Italic.otf') format('opentype')} @font-face {font-family: MJXc-TeX-size1-R; src: local('MathJax_Size1'), local('MathJax_Size1-Regular')} @font-face {font-family: MJXc-TeX-size1-Rw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Size1-Regular.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Size1-Regular.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Size1-Regular.otf') format('opentype')} @font-face {font-family: MJXc-TeX-size2-R; src: local('MathJax_Size2'), local('MathJax_Size2-Regular')} @font-face {font-family: MJXc-TeX-size2-Rw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Size2-Regular.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Size2-Regular.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Size2-Regular.otf') format('opentype')} @font-face {font-family: MJXc-TeX-size3-R; src: local('MathJax_Size3'), local('MathJax_Size3-Regular')} @font-face {font-family: MJXc-TeX-size3-Rw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Size3-Regular.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Size3-Regular.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Size3-Regular.otf') format('opentype')} @font-face {font-family: MJXc-TeX-size4-R; src: local('MathJax_Size4'), local('MathJax_Size4-Regular')} @font-face {font-family: MJXc-TeX-size4-Rw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Size4-Regular.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Size4-Regular.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Size4-Regular.otf') format('opentype')} @font-face {font-family: MJXc-TeX-vec-R; src: local('MathJax_Vector'), local('MathJax_Vector-Regular')} @font-face {font-family: MJXc-TeX-vec-Rw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Vector-Regular.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Vector-Regular.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Vector-Regular.otf') format('opentype')} @font-face {font-family: MJXc-TeX-vec-B; src: local('MathJax_Vector Bold'), local('MathJax_Vector-Bold')} @font-face {font-family: MJXc-TeX-vec-Bx; src: local('MathJax_Vector'); font-weight: bold} @font-face {font-family: MJXc-TeX-vec-Bw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Vector-Bold.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Vector-Bold.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Vector-Bold.otf') format('opentype')}  xCor=((12+7)//2,(5-2)*((8-3)//2),(((3+4)*((7+4)*2))%(8*(5-3)), (5*(3+2)//(2*(2+3)))),(2*(8-1)))  yCor=(23,25,26,28,30)  print(xCor,yCor)  Lst={"A":0,"B":1,"C":2,"D":3,"E":4}  inp=input("Pick from A to E")  if inp not in Lst:  print("Error")  inp="A"  val=Lst[inp]  sze=xCor[val]*yCor[val]  print(sze)  import numpy as np  np.random.normal(size=sze) 

The error sneaks in on the first line.

xCor=(9, 6, (10, 2), 14)

This is hidden by the brackets being used for tuples and precedence.

The next part of the error occurs at

 sze=xCor[val]*yCor[val] 

In python, the product of an integer and a tuple is a tuple.  >>> 3*4  12  >>> 3*(1,2)  (1, 2, 1, 2, 1, 2) 

This is far from the only case where python is slack with typing. You can multiply a Boolean by a string or add two lists or take a string modulo a tuple.

The final error comes with the numpy.random.normal function. It takes in a size. if that size is an integer, it makes a 1D array of that length, if it is a tuple, it creates a multidimensional array, with dimensions from the tuple. So if you enter "C", this piece of code produces a 52D array containing 2026=6710886400000000000000000000000000 random numbers. This causes your system to run out of memory and crash.

This is the structure of a cascading failure chain. Something goes wrong somewhere, but it isn't caught by the error correction mechanism and dealt with, instead it triggers something else to go wrong, and then another thing. Here going wrong means going outside the context that the programmer was thinking of when they wrote the code.

The basic problem was that the programming language was dynamically typed, so if you get passed a variable foo from another part of the program, it could be an Int or String or List or anything. The next problem comes from giving several different functions the same name. Multiplying integers and repeating lists are entirely different functions. If a programer relies on the fact that the same symbol * does both, they are being "clever" and probably producing confusing code.

The numpy.random.normal is a less egregious version of this, making a random array from a list and from a tuple a subtly different.

Hacking is the art of finding code execution paths not envisioned by the programmer.

All this means that most long and complex python program is likely to be hackable.

Haskel takes a different approach. In Haskel all the variables have types deduced at compile time, if you try any operation that doesn't make sense, the compiler stops it.

The python methodology is "Run any piece of code that is arguably meaningful".

The Haskel methodology is "Don't run any piece of code that's arguably meaningless".

The paranoid error detection of Haskel makes it harder to write code that seams to work, but easier to make a complex piece of code work reliably.



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Online Zoom Meetup, April 5th - 10:30 PST

28 марта, 2020 - 21:39
Published on March 28, 2020 6:39 PM GMT

I attended a Zoom meetup last week hosted by LessWrong Israel.

We had over 60 people join up and it was a lot of fun. The session worked like this: Volunteers took 4 minutes discussing or explaining a non-COVID-19 topic of their choice. Subjects included the strange history of a Japanese rice market, an ambitious attempt to bring back the Charleston after a century-long quiescence, a lesson on how to be a good DnD player, and an explanation of a counterintuitive recreational maths problem involving the probability of rolling "666" vs "456". (The Kabbalistic implications of this are left as an exercise to the reader.)

Then after time was up we voted, and if the crowd voted "yes" the speaker got another 3 minutes to continue their talk. After 90 minutes, we then ended the session but anyone who felt like hanging out and talking was welcome to.

If after reading this you are sad you didn't participate, then you are in luck. Provided I get enough interest, I will be hosting a similar meetup on Sunday at 10:30 PST.

Please click here to register:https://forms.gle/p1X1hmB5azpeSRvn7



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Iceland's COVID-19 random sampling results: C19 similar to Influenza

28 марта, 2020 - 21:26
Published on March 28, 2020 6:26 PM GMT

deCODE genetics has tested a random sample of about ~5K Icelanders for COVID-19 and about 0.9% tested positive, which indicates at least ~3K true infections in a population of ~330K, and perhaps more like ~6K if we consider failed tests for those who already recovered and general false negatives.

Iceland has only 2 deaths so far for a naive IFR in the range of 0.06% or less. However they have 6 patients in ICU (Iceland data), which has about a 30% fatality rate, so we can estimate a few more deaths in the coming weeks and that stills puts average IFR in the ~0.1% range, same as influenza.

The bayesian posterior odds ratio here is over 1 million to 1 in favor of ~0.1% IFR vs 1% IFR. In other words this single data set strongly rules out IFR higher than influenza.

It also agrees with the Diamond Princess data which rules out IFR much higher than influenza. (see my analysis here, or a more detailed analysis here) In that same post I also arrived at a similar conclusion by directly estimating under-reporting (the infection/case ratio) by comparing the age structure of confirmed cases to the age structure of the population and assuming uniform or slightly age-dependent attack rates similar to other viruses. That model predicts under-reporting of ~20X or more in the US, so it's not surprising that the under-reporting in Iceland is still in the ~4X range.

The infection hospitalization rate of COVID-19 in Iceland is also in the vicinity of ~1% or less, similar to influenza.

This also puts bounds on how widespread C19 can be - with IHR and IFR both similar to influenza, there couldn't be tens of millions of infected in the US as of a few weeks ago or we would be seeing considerably more hospitalizations and deaths than we do.

The 'common cold' is actually caused by over 200 virus strains of different orders, so I wonder if years from now SARS-CoV-2 will be lumped in as a non-influenza virus strain in the 'flu' category.



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Solipsism is Underrated

28 марта, 2020 - 21:09
Published on March 28, 2020 6:09 PM GMT

Consider two simple, non-exhaustive theories.

Theory 1, Strong Materialism: The only ontological primitive is matter. This is to say that there is nothing but physical things, and everything that happens can be reduced down to the material. Minds and consciousness must then be some emergent phenomenon based on matter. For example, some people who take this view speculate that consciousness may be “what an algorithm implemented on a physical machine (like your brain) feels like from the inside.”

Theory 2, Strong Solipsism: The only ontological primitive is my own mind. This is to say that there is nothing (or at least nothing worth believing in) but mental phenomena. Someone who takes this view might say that they have no good reason to believe that their experiences have a physical antecedent, and everything that exists is just what’s going on for them mentally. People with this view might point out that perceptions of things outside themselves don’t actually indicate those things — just the perceptions themselves.

There are also dualistic theories which assert the existence of both physical and mental primitives, but I don’t want to focus on them here, and they’re not too popular among the LessWrong crowd anyway. There are a series of problems with different forms of dualism involving the prior complexity of believing in multiple ontological primitives as well some curious means by which the physical and mental interact. It's generally agreed that dualistic theories would force us to believe in more unlikely phenomena than either materialism or solipsism and aren’t comparatively plausible.

My impression is that most people who I’ve listened to or read from who have discussed these ideas (including Brian Tomasik and Eliezer Yudkowsky), seem to prefer materialism. There are two good reasons people have for this. First, even though when I perceive something, it does not with certainty imply the existence of that thing (only of that perception), it is perfectly consistent with the existence of that thing. Second, I observe many people other than myself, and their behavior and feelings seem to be a lot like my own. Given both of these observations, the likelihood in Bayes rule for materialism is relatively high, while for solipsism, it’s not.

I think that these two points are strong reasons to suspect that materialism is a good theory and may have an advantage over solipsism. But it seems to me that when many people discuss the question, they mention these two points, miss applying a crucial counterpoint, and go along discussing metaphysics as if solipsism weren’t worth much consideration. I think this is a mistake.

Anyone who supports materialism has to bite a bullet. It implies that somehow, someway consciousness and qualia are phenomena that reduce down to the activity of physical systems. From a Newtonian perspective, atoms are much like billiard balls, bouncing around together, and from a quantum perspective, they are waves/particles interacting through forces and entanglements. But using either interpretation, how puzzling is the view, that the activity of these little material things somehow is responsible for conscious qualia? This is where a lot of critical thinking has led many people to say things like “consciousness must be what an algorithm implemented on a physical machine feels like from the ‘inside.’” And this is a decent hypothesis, but not an explanatory one at all. The emergence of consciousness and qualia is just something that materialists need to accept as a spooky phenomenon. It's not a very satisfying solution to the hard problem of consciousness. This belief in some mysterious ability for the mental to supervene on the physical is almost as ad hoc as the belief that dualists have in immaterial minds!

Suppose that you update on the evidence that you experience conscious qualia and your various perceptions about the world. How do the two theories compare? Both of them assume only a single primitive, be it the material or the mental (a huge advantage of either of these theories over dualism). But conditioning on the existence of consciousness, materialism must assume the existence of a strange phenomenon whereby physical things somehow cause qualia, and solipsism doesn’t do a good job of accounting for much of the structure in observations and your perception of other people much like yourself. In this sense, materialism has a relatively low prior and solipsism has a relatively low likelihood — qualitatively, at least.

Comparing these two posteriors quantitatively is hard, but it’s not a lopsided debate like I think many people assume. There’s definitely a huge advantage that solipsism has over materialism. So I recommend taking it seriously.



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Bogus Exam Questions

28 марта, 2020 - 15:56
Published on March 28, 2020 12:56 PM GMT

Take a look at this multiple choice question from the Open University BSc on psychology. Can you tell what is wrong with it. This is sampled from a set of 15 questions, some of the others aren't this bad, some are guessing the teachers password. One of the questions requires that you know that statistically significant means p<0.05 and can look at a table of p values and say which numbers are less than 0.05.

An educational psychologist believes that an individual's reading speed (in words per minute) and general comprehension abilities (scored out of 10) may be related to how well they do on a timed exam. To study the relative importance of these variables and the association between them, she runs a multiple regression and produces the following predictive model for exam score: Exam Score =7.78 + (0.05*Reading Speed)+(5.77*Comprehension) What exam score would you expect students to achieve if they have a reading speed of 120 w.p.m and a comprehension score of 5?
Select one:
o 4726
o 55.67
o 66.44
o 42.63

What level of understanding is necessary to fully understand the question?

From a mathematicians perspective, Multiple linear regression is an algorithm based on variational calculus (Optimizing over a space of functions), to select the function that maximizes the probability density that a model consisting of a linear function from the vector space .mjx-chtml {display: inline-block; line-height: 0; text-indent: 0; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 100%; font-size-adjust: none; letter-spacing: normal; word-wrap: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0; min-height: 0; border: 0; margin: 0; padding: 1px 0} .MJXc-display {display: block; text-align: center; margin: 1em 0; padding: 0} .mjx-chtml[tabindex]:focus, body :focus .mjx-chtml[tabindex] {display: inline-table} .mjx-full-width {text-align: center; display: table-cell!important; width: 10000em} .mjx-math {display: inline-block; border-collapse: separate; border-spacing: 0} .mjx-math * {display: inline-block; 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src: local('MathJax_Vector Bold'), local('MathJax_Vector-Bold')} @font-face {font-family: MJXc-TeX-vec-Bx; src: local('MathJax_Vector'); font-weight: bold} @font-face {font-family: MJXc-TeX-vec-Bw; src /*1*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/eot/MathJax_Vector-Bold.eot'); src /*2*/: url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/woff/MathJax_Vector-Bold.woff') format('woff'), url('https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/fonts/HTML-CSS/TeX/otf/MathJax_Vector-Bold.otf') format('opentype')} R3 to R plus a Gaussian random variable (with arbitrary standard deviation, that term happens to cancel out) assigns to the observed data. This involves function spaces, matrix inversions, multivariate integrals ect. To understand the mathematical structure that leads up to multivariate regression, you need the idea of jacobians and vector calculus just to integrate your e−12x2 to find the normalizing constant on your Gaussian random variables. You need continuus probability spaces, but probability isn't defined over arbitrary sets of real numbers, so you need sigma algebras, which brings you to set theory. You need to prove that the integrals exist, that the optimum slope exists and is unique, ect.

In short you need to understand a lot of maths to deeply understand what is going on.

How much understanding do you need to get the answer right. Suppose you have basic English comprehension, but all you know about the symbols "385+*)" is that they are some mysterious code that you can type into a calculator and it will reply in the same code.

You know that the answer has to be in this mysterious code, and the calculator doesn't have buttons for letters. You know its asking for an exam score, so you type in the code for "Exam score", but replacing the word "Reading speed" with the mysterious symbols "120", and the word "Comprehension" with the symbol "5".

Your calculator spits out an answer, it is one of the options available, you put it down. (You get an exact answer, no rounding needed)

Lets suppose your grasp of English was little better than your grasp of arithmetic.

You have no idea what an "educational psychologist" is.

You have a rough grasp of capital letters, you know that the first letter in words sometimes looks big or funny, enough to suspect that "Reading Speed" and "reading speed" are the same thing. None of the mysterious numbery things in the question match any of the answers, so you try typing the big numbery thing into a calculator. The calculator doesn't have any lettery buttons, so you replace the lettery things with the numbery things that are near them in the text. If you guess the wrong numbery thing the first time, you don't get an answer on the list, so if you know what a multiple choice test is, you will know to try another.

Maybe I am being a little scathing there, I am certainly assuming that the hypothetical person answering the question knows some exam technique, and are able go along with plausible guesses. But I would expect most people who knew basic English and arithmetic to be able to answer it correctly.

The basic problem is

An exam question only measures if you have enough understanding to answer it correctly.

The amount of understanding needed to answer a question can be lower than it appears.

The question references all sorts of advanced maths, giving the appearance of serious academic learning, but instead of asking you to show an understanding of that maths, it asks you something much simpler.

This is like guessing the teachers password, except that the password is a procedure, not a direct answer.



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Reminder: Blog Post Day II today!

28 марта, 2020 - 14:35
Published on March 28, 2020 11:35 AM GMT

Reminder: Blog Post Day II is happening today! Come join us online if you want to try to get a blog post done today.



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What software projects would be helpful for different groups?

28 марта, 2020 - 10:50
Published on March 28, 2020 7:50 AM GMT

There are various meetups around the world that work on altruistic software development. Random Hacks of Kindness is at the top of my mind at the moment.

The main site appears to be down at the moment, but the Australian and Canadian sites are still up, and the Australian one is asking for projects which help with the COVID-19 response.

That got me wondering. What software projects would be high leverage and not currently saturated? Which of them are amenable to being worked on by groups of developers with mixed skills and backgrounds?

This can probably be broken down further into software for different groups. Healthcare workers probably have different needs in this time than people who are struggling to make the case for working from home. My gut feeling is that efforts that helps with social support and mental health support will also have high value over time.



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mind viruses about body viruses

28 марта, 2020 - 07:20
Published on March 28, 2020 4:20 AM GMT

I was going to write this as a Slate Star Codex comment, but I’m going to make it a tumblr post tagging @slatestarscratchpad instead, since experience suggests it’s likely to be more widely and carefully read in this form.  (Crossposting to LW too, so you may be reading this there, possibly with mangled formatting.)

The idea frontier

I am getting more and more concerned about the “information epidemiology” of the public conversation about Covid-19.

Here are some distinctive features I see in the public conversation:

1. Information intake must be triaged.

There is a very large amount of new publicly available information every day.  There are no slow news days.  “Keeping up with the story” in the way one would keep up with an evolving news story would be a full-time job.  

Many of us do not have time to do this, and I imagine many of those who do have time cannot tolerate the experience in practice.  In fact, there can be a tradeoff between one’s level of personal involvement in the crisis and one’s ability to “follow it” as a news story.

(I work for a telemedicine company, and after a day of dealing with the ever-changing impacts of Covid-19 on my work, I have relatively little patience left to read about its ever-changing impacts on absolutely everything else.  That’s just me, though, and I realize some people’s mental bandwidth does not work like this.)

2. Abstractions are needed, and the relevant abstractions are novel and contested.

Crucial and time-sensitive decisions must be made on the basis of simulations, abstract mental models, and other intellectual tools.

In some sense this is true of everything, but in most cases we have a better sense of how to map the situation onto some large reference class of past intellectual work.  When there is an economic downturn, the standard macroeconomic arguments that have existed for many decades pop back up and make the predictable recommendations they always make; even though there is no expert consensus, the two or three common expert stances are already familiar.

With Covid-19, this is not so.  All the intervention types currently under discussion would be, in their own ways, unprecedented.  As it struggles to follow the raw facts, the general public is also struggling to get its head around terms and concepts like “suppression,” “containment,” “contact tracing,” etc. which were (in the relevant senses) not part of our mental world at all until recently.

Thus, relative to most policy debates, this one has a strange frontier energy, a sense that we’re all discovering something for the first time.  Even the professional epidemiologists are struggling to translate their abstract knowledge into brief-but-clear soundbites.  (I imagine many of them have never needed to be public communicators at this kind of scale.)

3. There is no division of labor between those who make ideas and those who spread them.

There is a hunger for a clear big picture (from #1).  There are few pre-established intellectual furnishings (#2).  This means there’s a vacuum that people very much want to fill.  By ordinary standards, no one has satisfying answers, not even the experts; we are all struggling to do basically the same intellectual task, simultaneously.

None of us have satisfying answers – we are all the same in that respect.  But we differ in how good we are at public communication.   At communicating things that sound like they could be answers, clearly, pithily.  At optimizing our words for maximum replication.

It is remarkable to me, just as a bare observation, that (in my experience) the best widespread scientific communication on Covid-19 – I mean just in the sense of verbal lucidity and efficiency, effective use of graphs, etc., not necessarily in the sense of accuracy or soundness – has been done by Tomas Pueyo, a formerly obscure (?) expert on … viral marketing.

(To be clear, I am not dismissing Pueyo’s opinions by citing his background.  I am hypothesizing his background explains the spread of his opinions, and that their correctness level has been causally inert, or might well have been.)

The set of ideas we use to understand the situation, and the way we phrase those ideas, is being determined from scratch as we speak.  Determined by all of us.  For the most part, we are passively allowing the ideas to be determined by the people who determine ideas in the absence of selection – by people who have specialized, not in creating ideas, but in spreading them.

4. Since we must offload much of our fact-gathering (#1) and idea-gathering (#2) work onto others, we are granting a lot on the basis of trust.

Scott’s latest coronavirus links post contains the following phrases:

Most of the smart people I’ve been reading have converged on something like the ideas expressed in […]

On the other hand, all of my friends who are actually worried about getting the condition are […]

These jumped out at me when I read the post.  They feel worrying like an “information cascade” – a situation where an opinion seems increasing credible as more and more people take that opinion partially on faith from other individually credible people, and thus spread it to those who find them credible in turn.

Scott puts some weight on these opinions on the basis of trust – i.e. not 100% from his independent vetting of their quality, but also to some extent from an outside view, because these people are “smart,” “actually worried.”  Likelier to be right than baseline, as a personal attribute.  So now these opinions get boosted to a much larger audience, who will take them again partially on trust.  After all, Scott Alexander trusts it, and he’s definitely smart and worried and keeping up with the news better than many of us.

What “most of the smart people … have been converging on,” by the way, is Tomas Pueyo’s latest post.

Is Tomas Pueyo right?  He is certainly good at seeming like a “smart” and “actually worried” person whose ideas you want to spread.  That in itself is enough.  I shared his first big article with my co-workers; at that time it seemed like a shining beacon of resolute, well-explained thought shining alone in a sea of fog.  I couldn’t pull off that effect as well if I tried, I think – not even if the world depended on it.  I’m not that good.  Are you?

My co-workers read that first post, and their friends did, and their friends.  If you’re reading this, I can be almost sure you read it too.  Meanwhile, what I am not doing is carefully reading the many scientific preprints that are coming out every week from people with more domain expertise, or the opinions the same people are articulating in public spaces (usually, alas, in tangled twitter threads).  That’s hard work, and I don’t have the time and energy.  Do you?

I don’t know if this is actually an effective metaphor – after all, I’m not a viral marketer – but I keep thinking of privilege escalation attacks.

It is not a bad thing, individually, to place trust some in a credibly-sounding person without a clear track record.  We can’t really do otherwise, here.  But it is a bad thing when that trust spreads in a cascade, to your “smartest” friends, to the bloggers who are everyone’s smartest friends, to the levers of power – all on the basis of what is (in every individual transmission step) a tiny bit of evidence, a glimmer of what might be correctness rising above pure fog and static.  We would all take 51% accuracy over a coin flip – and thus, that which is accurate 51% of the time becomes orthodoxy within a week.

Most of the smart people you’ve been reading have converged on something like … 

#FlattenTheCurve: a case study of an imperfect meme

Keeping up with the lingo

A few weeks ago – how many? I can’t remember! – we were all about flattening the curve, whatever that means.

But this week?  Well, most of the smart people you’ve been reading have converged on something like: “flattening” is insufficient.  We must be “squashing” instead.  And (so the logic goes) because “flattening” is insufficient, the sound byte “flatten the curve” is dangerous, implying that all necessary actions fall under “flattening” when some non-flattening actions is also needed.

These are just words.  We should be wary when arguments seem to hinge on the meaning of words that no one has clearly defined.

I mean, you surely don’t need me to tell you that!  If you’re reading this, you’re likely to be a veteran of internet arguments, familiar from direct experience and not just theory with the special stupidity of merely semantic debates.  That’s to say nothing of the subset of my readership who are LessWrong rationalists, who’ve read the sequences, whose identity was formed around this kind of thing long before the present situation.  (I’m saying: you if anyone should be able to get this right.  You were made for this.)

It’s #FlattenTheCurve’s world, we just live in it

What did “flatten the curve” mean?  Did it mean that steady, individual-level non-pharmaceutical interventions would be enough to save hospitals from overload?  Some people have interpreted the memetic GIFs that way, and critiqued them on that basis.

But remember, #FlattenTheCurve went viral back when fretting about “coronavirus panic” was a mainstream thing, when people actually needed to be talked into social distancing.  The most viral of the GIFs does not contrast “flattening” with some other, more severe strategy; it contrasts it with nothing.  Its bad-guy Goofus character, the foil who must be educated into flattening, says: “Whatever, it’s just a cold or flu.”

No one is saying that these days.  Why?  How did things change so quickly?  One day people were smugly saying not to panic, and then all of a sudden they were all sharing a string of words, a picture, something that captivated the imagination.  A meme performed a trick of privilege escalation, vaulted off of Facebook into the NYT and the WaPo and the WSJ and the public statements of numerous high officials.  Which meme? – oh, yes, that one.

We are only able to have this conversation about flattening-vs-squashing because the Overton Window has shifted drastically.  Shifted due to real events, yes.  But also due to #FlattenTheCurve.  The hand you bite may be imperfect, but it is the hand that feeds you.

Bach, the epidemiologists, and me

Joscha Bach things #FlattenTheCurve is a “lie,” a “deadly delusion.”  Because the GIF showed a curve sliding under a line, yet the line is very low, and the curve is very high, and we may never get there.

Is he right?  He is definitely right that the curve is very low, and we may not slide under it.  Yet I was unimpressed.

For one thing, Bach’s argument was simply not formally valid: it depended on taking a static estimate of total % infected and holding it constant when comparing scenarios across which it would vary.

(This was one of several substantive, non-semantic objections I made.  One of them, the point about Gaussians, turned out to be wrong, in the sense that granting my point could not have affected Bach’s conclusion – not that Bach could have reached his conclusion anyway.  This argument was my worst one, and the only one anyone seemed to notice.)

Something also seemed fishy about Bach’s understanding of “flatten the curve.”  The very expert from whom he got his (misused) static estimate was still tweeting about how we needed to flatten the curve.  All the experts were tweeting about how we needed to flatten the curve.  Which was more plausible: that they were all quite trivially wrong, about the same thing, at once?  Or that their words meant something more sensible?

The intersection of “world-class epidemiologists” and “people who argue on twitter” have now, inevitably, weighed in on Bach’s article.  For instance:

And I can’t resist quoting one more Carl Bergstrom thread, this one about another medium post by a viral marketer (not the other one), making the exact same damn point I made about the static estimate:

Like me, these people make both substantive and semantic objections.  In fact, theirs are a strict superset of mine (see that last Bergstrom thread re: Gaussians!).

I am not saying “look, I was right, the experts agree with me, please recognize this.”  I mean, I am saying that.

But I’m also saying – look, people, none of this is settled.  None of us have satisfying answers, remember.  We are all stressed-out, confused glorified apes with social media accounts yelling at each other about poorly defined words as we try to respond to an invader that is ravaging our glorified-ape civilization.  Our minds cannot handle all this information.  We are at the mercy of viral sound bites, and the people who know how to shape them.

What is it the rationalists like to say?  “We’re running on corrupted hardware?”

Carl Bergstrom championed a meme, #FlattenTheCurve.  He believed would work, and I think it in fact did.  But Carl Bergstrom, twitter adept though he may be, is still someone whose primary career is science, not consensus-making.  In a war of memes between him and (e.g.) Tomas Pueyo, I’d bet the bank on Pueyo winning.

And that is frightening.  I like Pueyo’s writing, but I don’t want to just let him – or his ilk – privilege-escalate their way into effective command of our glorified ape civilization.

I want us to recognize the kind of uncertainty we live under now, the necessity for information and idea triage, the resulting danger of viral soundbites winning our minds on virality alone because we were too mentally overwhelmed to stop the spread … I want us to recognize all of that, and act accordingly.

Not to retreat into the comfort of “fact-checking” and passive consultation of “the experts.”  That was always a mirage, even when it seemed available, and here and now it is clearly gone.  All of us are on an equal footing in this new frontier, all of us sifting through Medium articles, twitter threads, preprints we half understand.  There are no expert positions, and there are too many facts to count.

Not to trust the experts – but to exercise caution.  To recognize that we are letting a “consensus” crystalize and re-crystalize on the basis of cute dueling phrases, simplified diagrams and their counter-simplified-diagrams, bad takes that at least seem better than pure white noise, and which we elevate to greatness for that alone.  Maybe we can just … stop.  Maybe we can demand better.  Wash our minds’ hands, too.

Our intellectual hygiene might end up being as important as our physical hygiene.  Those who control the levers of power are as confused and stressed-out as you are, and as ready to trust viral marketers with firm handshakes and firm recommendations.  To trust whichever sound byte is ascendant this week.

Thankfully, you have some measure of control.  Because we are all on flat ground in this new frontier, your social media posts are as good as anyone’s; you can devote your mind to making ideas, or your rhetorical skill to promoting specifically those ideas you have carefully vetted.  You can choose to help those with power do better than the status quo, in your own little way, whatever that may be.  Or you can choose not to.

Okay, words aside, does the right strategy look like the famous GIF taken literally, or like a feedback system where we keep turning social distancing on and off so the graph looks like a heart rate monitor, or like a “hammer” reset followed by a successful emulation of South Korea, or

I don’t know and you don’t know and Tomas doesn’t know and Carl doesn’t know.  It’s hard!  I’m hadn’t even heard of “R_0” until like two months ago!  Neither had you, probably!

Marc Lipsitch’s group at Harvard has been putting out a bunch of preprints and stuff that look reputable to me, and are being widely shared amongst PhDs with bluechecks and university positions.  Their most recent preprint, from 3 days ago, appears to be advocating the heart rate monitor-ish thing, so yay for that, maybe.  But … this sounds like the same information cascade I warned against, so really, I dunno, man.

However, I will suggest that perhaps the marginal effect of sharing additional reputable-seeming takes and crystalizing weekly orthodoxies is negative in expectation, given an environment saturated with very viral, poorly vetted words and ideas.

And that your best change of a positive marginal impact is to be very careful, like the people who won’t trust any medical intervention until it has 50+ p-hacked papers behind it, has been instrumental in the minting of many PhDs, and has thereby convinced the strange beings at FDA and the Cochrane Collaboration who move at 1/100 the speed of you and me.  Not because this is globally a good way to be, but because it locally is – given an environment saturated with very viral, poorly vetted words and ideas.

That you should sit down, take the outside view, think hard about whether you can make a serious independent intellectual contribution when literally everyone on earth, basically, is trying to figure out the same thing.

And you know, maybe you are really smart!  Maybe the answer is yes!  If so, do your homework.  Read everything, more than I am reading, and more carefully, and be ready to show your work.  Spend more time on this than the median person (or me) is literally capable of doing right now.  This is the value you are claiming to provide to me.

If you can’t do that, that is fine – I can’t either.  But if you can’t do that, and you still boost every week’s new coronavirus orthodoxy, you are an intellectual disease vector.  Don’t worry: I will hear it from other people if I don’t hear it from you.  But you will lend your credibility to it.  Whatever trust I place in you will contribute to the information cascade.

This work, this hard independent work collecting lots of raw undigested information, is actually what Tomas Pueyo seems to be doing – I mean, apart from framing everything in a very viral way, which is why you and I know of his work.  We are saturated with signal-boosts of the few such cases that exists.  We do not need more signal-boosts.  We need more independent work like this.  Please do it.  Or, if not that, then be like the lady in that very problematic GIF: don’t panic, but be careful, wash your mind’s hands, and (yes) flatten the intellectual curve.



Discuss

What can we call the mistaken belief that something can't be measured?

28 марта, 2020 - 03:16
Published on March 27, 2020 10:10 PM GMT

In his book How to Measure Anything, Douglas W. Hubbard defines measurement as _a quantitative reduction in uncertainty_. He also shows how anything can be measured, i.e. how it's always possible to quanitatively reduce uncertainty.


However, it's common for people to flat-out believe that many things — such as the value of a human life — can't be measured. I believe they are wrong, and I would like a name for being wrong in this way. Is there already a name for this fallacy? If so, what is it? If not, what do you think of the _immeasurability fallacy_? Or do you have other ideas?



Discuss

The case for C19 being widespread

28 марта, 2020 - 03:07
Published on March 28, 2020 12:07 AM GMT

GDoc version

Epistemic status: very, very uncertain. Please continue following official advice like social distancing etc.

I've seen all the previous discussions (including in this thread and on Tyler Cowen's blog, but remain unconvinced]

--

A preprint from 24/03 by Gupta et al. at Oxford[1] suggests that the current data on C19 is consistent with both:

  • Few infections, low infectiousness (r0), and high infection fatality rate (IFR)
  • Widespread actual (asymptomatic) infections, high r0 and low IFR

For instance, the authors suggest that if the IFR is low and C19 is very infectious, it is possible that by 19/03, 36%-68% of the UK population would have already been infected with C19. The ongoing epidemics in the UK and Italy started at least a month before the first reported death.

This study has been criticized, but scientists agree that serological assays will show whether this hypothesis is true.[2], [3]

Here I make the strongest possible case that C19 is widespread, r0 is underestimated and IFR is low.

I base this on the following:

  • Much C19 transmission might be asymptomatic[4] and presymptomatic.[5],[6]
  • Tim Spector, professor of genetic epidemiology a King's College London, finds that
    • 10% of 650,000 UK users of their C19 symptom tracker app showed mild symptoms. Thus 6.5m people in UK are infected, not taking into account asymptomatic cases
  • A preprint from 26/03 by epidemiologists Gutierrez et al.[7], Professor and Chair of Mathematics at University of Texas at San Antonio (Google Scholar Profile) suggests
    • An R0 between 5.5 and 25.4[8], if you account for asymptomatic spread. In this scenario, the peak of symptomatic infections is reached in 36 days with approximately 9.5% of the entire population showing symptoms.
    • The authors argue that it’s unlikely for a pathogen to blanket the planet in three months with an R0= ~3 and that it has to be more contagious than measles, which has an R0 of 18.
  • A preprint from 13/03 by Chowell et al., Professor & Chair - Georgia State University School of Public Health suggesting (GScholar profile first author who has written 2 papers on the Diamond Princess, senior author quoted in the NYT) suggests that
    • r0=5.20 (95%CrI: 5.04-5.47)
    • IFR=0.12% (95%CrI: 0.08-0.17%), several orders of magnitude smaller than the crude CFR estimated at 4.19%.[9]
    • ~20% of the all people in Wuhan were infected on Jan 23rd (~2 million infections)
  • A preprint from 24/03 by French epidemiologists[10] (Google Scholar profile) suggesting:
    • “The actual infections France is probably much higher than the observations: we find here a factor ×15 (95%-CI: 4 − 33), which leads to a 5.2/1000 mortality rate (95%-CI: 1.5/1000 − 11.7/1000) at the end of the observation period. We find a R0 of 4.8, a high value which may be linked to the long viral shedding period of 20 days r0=4.8”
  • Oxford University Evidence Service meta-analysis suggests that as of 22/03 that the IFR=~0.29% (95% CI, 0.25 to 0.33).[11] Widespread testing (which isn’t random) in Iceland suggests an even lower IFR.
  • A British Medical Journal editorial from 20/03 arguing that C19 fatality is likely overestimated [12]
  • The Imperial study is based on “thousands of lines of undocumented C [code] from 13+ years ago to model flu pandemics”[13]
  • Dengue tests react to C19 and many could be false positives according to a Lancet paper[14]
    • Dengue fever crisis grips Latin America | News
    • Through the week ending March 13, Paraguay has reported 203,922 total dengue fever cases, including 51 deaths. This compares to 669 dengue cases reported during the same period in 2019."[15]
    • Singapore which is said to have very good containment of C19, reports a recent dengue outbreak (4000 cases) doubled from previous year[16]
    • There were a few dengue in Australia and Florida where it is unusual[17]
  • High proportion of special populations are infected (celebrities, athletes and politicians).[18] For instance, very many Iranian politicians have C19.[19] This suggests that if the whole population had access to frequent tests like those special groups would have, then we would see many more cases. Fatalities are also very high amongst people with very high age and many comorbidities, suggesting that there are many asymptomatic infections amongst the young.
  • C19 has been detected in wastewater in the Netherlands. If the test is not very sensitive, this would suggest C19 is widespread.
  • PCR test have a high false negative rate
    • They can only detect the virus for ~1 week
    • The accuracy of similar tests for influenza is generally 50–70%.
    • Difficulties in False Negative Diagnosis of Coronavirus Disease 2019: A Case Report. Note that this was a highly symptomatic person.
    • One person had persistent negative swab, but tested positive through fecal samples.[21]
    • “If the samples are not correctly stored and handled, the test may not work. There has also been some discussion about whether doctors testing the back of the throat are looking in the wrong place. This is a deep lung infection rather one in the nose and throat.”[22]
    • 71% accurate the first time people are tested.  The other 29%, the test showed negative even though they really had it.[23]
  • Infections in China might be underestimated because:

[1] Lourenco J, Paton R, Ghafari M, et al. Fundamental principles of epidemic spread highlight the immediate need for large-scale serological surveys to assess the stage of the SARS-COV-2 epidemic. https://www.dropbox.com/s/oxmu2rwsnhi9j9c/Draft-COVID-19-Model%20%2813%29.pdf

[2] "Covid-19: experts question analysis suggesting half ... - The BMJ." https://www.bmj.com/content/368/bmj.m1216.full.pdf. Accessed 25 Mar. 2020.

[3] "expert reaction to unpublished paper modelling what ...." 25 Mar. 2020, https://www.sciencemediacentre.org/expert-reaction-to-unpublished-paper-modelling-what-percentage-of-the-uk-population-may-have-been-exposed-to-covid-19/. Accessed 25 Mar. 2020.

[4] "Presumed Asymptomatic Carrier Transmission of COVID-19 ...." 21 Feb. 2020, https://jamanetwork.com/journals/jama/fullarticle/2762028. Accessed 18 Mar. 2020.

[5] "Potential Presymptomatic Transmission of SARS-CoV ... - NCBI." https://www.ncbi.nlm.nih.gov/pubmed/32091386. Accessed 18 Mar. 2020.

[6] "Transmission interval estimates suggest pre-symptomatic ...." 6 Mar. 2020, https://www.medrxiv.org/content/10.1101/2020.03.03.20029983v1. Accessed 18 Mar. 2020.

[7] "Investigating the Impact of Asymptomatic Carriers on COVID ...." 20 Mar. 2020, https://www.medrxiv.org/content/10.1101/2020.03.18.20037994v1. Accessed 25 Mar. 2020.

[8] Investigating the Impact of Asymptomatic Carriers on  COVID-19 Transmission

[9] "Early epidemiological assessment of the transmission ...." 13 Mar. 2020, https://www.medrxiv.org/content/10.1101/2020.02.12.20022434v2. Accessed 25 Mar. 2020.

[10] "Mechanistic-statistical SIR modelling for early estimation of the ...." 24 Mar. 2020, https://www.medrxiv.org/content/10.1101/2020.03.22.20040915v1. Accessed 27 Mar. 2020.

[11] "Global Covid-19 Case Fatality Rates - CEBM." 17 Mar. 2020, https://www.cebm.net/archives/covid-19/global-covid-19-case-fatality-rates. Accessed 27 Mar. 2020.

[12] "Covid-19 fatality is likely overestimated | The BMJ." 20 Mar. 2020, https://www.bmj.com/content/368/bmj.m1113. Accessed 27 Mar. 2020.

[13] "neil_ferguson on Twitter: "I'm conscious that lots of people ...." 22 Mar. 2020, https://twitter.com/neil_ferguson/status/1241835454707699713. Accessed 27 Mar. 2020.

[14] "Covert COVID-19 and false-positive dengue ... - The Lancet." https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30158-4/fulltext. Accessed 27 Mar. 2020.

[15] "Dengue outbreak in Paraguay: More than 200K cases ...." 24 Mar. 2020, http://outbreaknewstoday.com/dengue-outbreak-in-paraguay-more-than-200k-cases-reported-to-date-57202/. Accessed 27 Mar. 2020.

[16] "Dengue infections hit 4000, doubling from same period last year." 22 Mar. 2020, https://www.straitstimes.com/singapore/dengue-infections-hit-4000-doubling-from-same-period-last-year. Accessed 27 Mar. 2020.

[17] "Dengue cases in Townsville could potentially be ruled ... - ABC." 27 Mar. 2020, https://www.abc.net.au/news/2020-03-27/dengue-cases-in-townsville-could-potentially-be-ruled-outbreak/12096104. Accessed 27 Mar. 2020.

[18] "Celebrities, Athletes and Politicians With Coronavirus ...." https://www.nytimes.com/article/coronavirus-celebrities-actors-politicians.html. Accessed 27 Mar. 2020.

[19] "Iran's Coronavirus Problem Is a Lot Worse Than It Seems ...." 9 Mar. 2020, https://www.theatlantic.com/ideas/archive/2020/03/irans-coronavirus-problem-lot-worse-it-seems/607663/. Accessed 27 Mar. 2020.

[20] "Novel coronavirus found in wastewater | RIVM." 24 Mar. 2020, https://www.rivm.nl/node/153991. Accessed 26 Mar. 2020.

[21] "COVID-19 Disease With Positive Fecal and Negative ...." https://journals.lww.com/ajg/Citation/publishahead/COVID_19_Disease_With_Positive_Fecal_and_Negative.99371.aspx. Accessed 26 Mar. 2020.

[22] "Are coronavirus tests flawed? - BBC News." 13 Feb. 2020, https://www.bbc.com/news/health-51491763. Accessed 26 Mar. 2020.

[23] Modes of contact and risk of transmission in COVID-19 among close contacts

[24] "Life after lockdown: has China really beaten coronavirus ...." 23 Mar. 2020, https://www.theguardian.com/world/2020/mar/23/life-after-lockdown-has-china-really-beaten-coronavirus. Accessed 26 Mar. 2020.

[25] "How China's Coronavirus Incompetence Endangered the World." 15 Feb. 2020, https://foreignpolicy.com/2020/02/15/coronavirus-xi-jinping-chinas-incompetence-endangered-the-world/. Accessed 27 Mar. 2020.

[26] "Eighty percent of coronavirus tests 'donated' by China to ...." 25 Mar. 2020, https://www.washingtonexaminer.com/washington-secrets/80-of-virus-tests-donated-by-china-to-czechs-are-faulty. Accessed 27 Mar. 2020.



Discuss

What are the best online tools for meetups and meetings?

28 марта, 2020 - 01:58
Published on March 27, 2020 10:58 PM GMT

tl;dr – If you have tried at least three telepresence tools, explain which one is your favorite and why.

A key question for both remote organizations, and apparently all social life now, is "what tools can best keep me connected to people in the way that in-person-meetings used to."

There are plenty of tools available, ranging from videoconferencing (like Skype or Zoom) to video-games (like Minecraft). But it can be hard to evaluate them in isolation.

So instead of posting "Hey, I like X", this thread is modeled after The Best Textbooks on Any Subject – don't just post about a tool you like. Instead, compare that tool to two other tools, and explain what's superior about your favorite software.



Discuss

Is donating to AMF and malaria interventions the most cost-effective way to save lives from COVID-19?

28 марта, 2020 - 01:26
Published on March 27, 2020 10:25 PM GMT

This is a cross-post from the EA forum and wanted to gather the thoughts of LessWrong. I am new to both communities so I apologize in advance if I overstep any rules. If I have, please let me know!

Looking at WHO's recommendation to maintain malaria interventions and AMF's response to COVID-19, it sounds like reducing mortality of malaria can and will reduce mortality of COVID-19.

This seems to be based on the assumption that if you prevent a malaria patient from having to go to the hospital, then that frees up resources for them to focus on saving a COVID-19 patient.

So if we were to oversimplify this as an example:

Let's say a hospital has 50 beds. There are 50 COVID patients and 50 malaria patients. Thus, you can only save half of them. If we were able to prevent malaria in those 50 patients, then the hospital can allocate all 50 beds to the 50 COVID patients - thus, saving everyone.

Now, I'm very sure there's much more to consider than my oversimplification - so I would love to hear people's thoughts and be proven wrong!

---

EDIT: I reached out to AMF for further clarification and here is their response.

There are several ways in which reducing malaria – both morbidity and mortality – helps reduce the impact of COVID-19.First, if people are ill with malaria their immune system is less able to cope with the effect of COVID-19 so the impact of COVID-19 can be expected to be greater. This is consistent with those most at risk being people with ‘underlying health issues’. Increased malaria leads to a greater strain on already fragile health systems including taking up more intensive care beds.Second, if people are ill will malaria, whose symptoms are very similar to those of COVID (high fever), (“….the early symptoms of COVID-19, including fever, myalgia, and fatigue, might be confused with malaria and lead to challenges in early clinical diagnosis.” Source: Lancet article) the identification and management of COVID-19 is made more difficult. There is a greater risk of mis/under-diagnosis (treated as malaria when in fact COVID-19) or over-diagnosis (treated as COVID-19 and perhaps a bed in a hospital allocated, when malaria is the illness), which makes the management of COVID-19 more challenging.Third, if we delay desperately needed universal net coverage campaigns, and bednets are the most effective mechanism of preventing malaria, as well as other malaria control interventions, there is a significant risk, indeed a likelihood, that malaria will increase leading to further loss of life, illness, a greater strain on health systems trying to deal with COVID-19 as well as increased negative economic impact - if people are ill, they cannot farm, drive, teach, function.For these reasons and as the WHO advises, it is important that malaria control activities continue. These activities are likely to require sensible operational adjustments, including increased sanitizing measures and social distancing, to limit transmission risk.

Discuss

Coronavirus Research Ideas for EAs

28 марта, 2020 - 01:10
Published on March 27, 2020 10:10 PM GMT

Peter Hurford wrote a large, very comprehensive, research agenda over on the EA Forum. Here are all the questions: 

Meta-Research

1.) Just how bad are things right now? How bad might we expect it to get? What is the current state of play and what are various plausible scenarios forward? [PRIORITY]

2.) What paths to impact are available to us with regard to coronavirus related work? What is our rough guess of how this impact might compare to typical EA work?

3.) An insane amount of research is being produced at a rapid pace. How can we best consolidate and synthesize this information and get people up to speed quickly? [PRIORITY]

4.) An insane number of people are working hard on this, both inside and outside the EA movement. How should we best coordinate? [PRIORITY]

5.) What else could and should EAs do, other than these research questions?

6.) Are there places EAs should donate that focus on coronavirus response that are particularly promising to donate to, relative to existing charities EAs like?

7.) Does EA need a rapid response task force to coordinate inevitable future catastrophes? How can we be better prepared to respond to the next one?

8.) What do our biosecurity and pandemic prevention specialists think the rest of us should be doing right now?

Policy Response

9.) What, more precisely, is the “endgame scenario” for getting out of the coronavirus situation with minimal deaths? What kind of timeline might we be looking at?

10.) Will there be some situations or risks that could arise that make some of the desired endgames impossible or much more difficult to implement?

11.) How have various countries, states, counties, cities, private companies, non-profits, civil societies, etc. successfully or unsuccessfully handled the coronavirus policy response so far?

12.) How might we expect COVID to change policy advocacy over 2020-2022?

13.) What, if anything, can be done to change coronavirus response policy for the better? What about for future pandemics / crises?

14.) Low- and middle-income countries seem at particular risk of not being able to handle the coronavirus problem. How bad will this situation be? What should be done to mitigate it? Do we have any viable paths to impact?

15.) What is the actual cost-benefit of various pandemic responses? [PRIORITY]

16.) What opportunities does this give for us to improve institutions and policies more broadly?

17.) Are there any ballot initiatives we should consider for 2022 and 2024?

18.) Polling could be very valuable right now. What questions should we be asking the general public and how can we leverage their responses to effect change?

EA Community Health

19.) Does coronavirus pose a risk to the cohesion and stability of effective altruism movement? If so, how should we mitigate this? [PRIORITY]

20.) Are local groups still able to operate ok? What implications does this have for EA local groups strategy? Are any local groups at risk of collapse?

21.) A recession is something EA has never faced before. Could an associated fundraising shortfall lead to the collapse of any EA orgs? What can we do to mitigate this? [PRIORITY]

22.) Much EA-aligned “direct work” is severely disrupted or cannot happen. How does that affect these orgs? What should these orgs do differently? [PRIORITY]

23.) Many EAs and EA orgs are now suddenly working remotely for the first time. Do they have the resources they need to be effective?

24.) Are there other risks EAs should be preparing for that we aren’t?

25.) Could the EA movement use the existing groundswell of altruistic action to form better partnerships with non-EAs?

Existential Risk Implications

26.) Is this pandemic a catastrophic risk threat multiplier? How should this change EA’s approach to risk mitigation?

27.) How does this pandemic affect the balance of great powers? What implications does this have? Is this important to look into right now?

28.) What are the implications of widespread expansion of surveillance? Are there ways we can mitigate any risks?

29.) Could massive expansion of largely unrestricted funding to biolabs and other research produce any “dual-use” concerns?

30.) It seems like the world is now aware, perhaps for the first time in modern history, that catastrophic risks can happen. How should we seize this moment?

31.) What biosecurity policies should we try to implement?

32.) What does the COVID outbreak teach us retrospectively about how we should’ve handled this risk? Were the right systems in place?

Animal Welfare Implications

33.) It seems like the world is now aware, perhaps for the first time, that factory farming might pose severe health risks. This could be the biggest opportunity for a pro-animal campaign in modern history. However, mistiming this campaign could risk the biggest backlash to the animal welfare movement in modern history. Given this, how should we respond to this moment? [PRIORITY]

34.) How do we shift animal welfare work to the new online-only world and keep the animal movement from being curtailed?

35.) COVID has had implications for animal welfare. Does this create any new sources of animal suffering that we should take action on? Does it threaten to create any new risks that we can try to get ahead of?

36.) What will be the medium-term effect of COVID-19 and associated economic consequences on the demand for and growth of plant-based products?

Other Implications

37.) Does having widespread lockdowns change the balance of cause areas or create a “Cause X”?



Discuss

Has the effectiveness of fever screening declined?

28 марта, 2020 - 01:07
Published on March 27, 2020 10:07 PM GMT

On March 6th, jimrandomh predicted that the effectiveness of fever-screening for coronavirus would decline, because the virus would evolve to produce fever later or not at all. Has this happened in countries that have been liberally applying fever-screening?



Discuss

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