Scott Alexander

Scott Alexander's Comments

April Coronavirus Open Thread

No, it says:

The study design does not allow us to determine whether medical masks had efficacy or whether cloth masks were detrimental to HCWs by causing an increase in infection risk. Either possibility, or a combination of both effects, could explain our results. It is also unknown whether the rates of infection observed in the cloth mask arm are the same or higher than in HCWs who do not wear a mask, as almost all participants in the control arm used a mask. The physical properties of a cloth mask, reuse, the frequency and effectiveness of cleaning, and increased moisture retention, may potentially increase the infection risk for HCWs. The virus may survive on the surface of the facemasks,29 and modelling studies have quantified the contamination levels of masks.30 Self-contamination through repeated use and improper doffing is possible. For example, a contaminated cloth mask may transfer pathogen from the mask to the bare hands of the wearer. We also showed that filtration was extremely poor (almost 0%) for the cloth masks. Observations during SARS suggested double-masking and other practices increased the risk of infection because of moisture, liquid diffusion and pathogen retention.31 These effects may be associated with cloth masks... The study suggests medical masks may be protective, but the magnitude of difference raises the possibility that cloth masks cause an increase in infection risk in HCWs.
April Coronavirus Open Thread is skeptical of cloth masks. Does anyone have any thoughts on it, or know any other studies investigating this question?

April Coronavirus Open Thread

In most major countries, daily case growth has switched from exponential to linear, an important first step towards the infection being under control. See for more, you can change which countries are on the graph for more detail. The growth rate in the world as a whole has also turned linear, . Since this is growth per day, a horizontal line represents a linear growth rate.

If it was just one country, I would worry it was an artifact of reduced testing. Given almost every country at once, I say it's real.

The time course doesn't really match lockdowns, which were instituted at different times in different countries anyway. Sweden and Brazil, which are infamous for not taking any real coordinated efforts to stop the epidemic, are showing some of the same positive signs as everyone else - see - though the graph is a little hard to interpret.

My guess is that this represents increased awareness of social distancing and increased taking-things-seriously starting about two weeks ago, and that this happened everywhere at once because it was more of a media phenomenon than a political one, and the media everywhere reads the media everywhere else and can coordinate on the same narrative quickly.

April Coronavirus Open Thread

Thanks for the shout-out, but I don't think the thing I proposed there is quite the same as hammer and dance. I proposed lockdown, then gradual titration of lockdown level to build herd immunity. Pueyo and others are proposing lockdown, then stopping lockdown in favor of better strategies that prevent transmission. The hammer and dance idea is better, and if I had understood it at the time of writing I would have been in favor of that instead.

(there was an ICL paper that proposed the same thing I did, and I did brag about preempting them, which might be what you saw)

SSC - Face Masks: Much More Than You Wanted To Know

Sorry, by "complete" I meant "against both types of transmission". I agree it was confusing/wrong as written, so I edited it to say "generalized".

Can crimes be discussed literally?

Agreed, it seems very similar to (maybe exactly like) the "Martin Luther King was a criminal" example from there.

March Coronavirus Open Thread

China is following a strategy of shutting down everything and getting R0 as low as possible. This works well in the short term, but they either have to keep everything shut down forever, or risk the whole thing starting over again.

UK is following a strategy of shutting down only the highest-risk people, and letting the infection burn itself out. It's a permanent solution, but it's going to be really awful for a while as the hospitals overload and many people die from lack of hospital care.

What about a strategy in between these two? Shut everything down, then gradually unshut down a little bit at a time. Your goal is to "surf" the border of the number of cases your medical system can handle at any given time (maybe this would mean an R0 of 1?) Any more cases, and you tighten quarantine; any fewer cases, and you relax it. If you're really organized, you can say things like "This is the month for people with last names A - F to go out and get the coronavirus". That way you never get extra mortality from the medical system being overloaded, but you do eventually get herd immunity and the ability to return to normalcy.

This would be sacrificing a certain number of lives, so you'd only want to do it if you were sure that you couldn't make the virus disappear entirely, and sure that there wasn't going to be vaccine or something in a few months that would solve the problem, but it seems like more long-term thinking than anything I've heard so far.

I've never heard of anyone trying anything like this before, but maybe there's never been a relevant situation before.

The Critical COVID-19 Infections Are About To Occur: It's Time To Stay Home [crosspost]

It sounds like you've found that by March 17, the US will have the same number of cases that Italy had when things turned disastrous.

But the US has five times the population of Italy, and the epidemic in the US seems more spread out compared to Italy (where it was focused in Lombardy). This makes me think we might have another ~3 doubling times (a little over a week) after the time we reach the number of cases that marked the worst phase of Italy, before we get the worst phase here.

I agree that it's going to get worse than most people expect sooner than most people expect, and that now is a good time to start staying inside. But (and I might be misunderstanding) I'm not sure if I would frame this as "tell people to stay inside for the next five days", because I do think it's possible that five days from now nothing has gotten obviously worse and then people will grow complacent.

When to Reverse Quarantine and Other COVID-19 Considerations

Have you looked into whether cinchona is really an acceptable substitute for chloroquine?

I'm concerned for two reasons. First, the studies I saw were on chloroquine, and I don't know if quinine is the same as chloroquine for this purpose. They have slightly different antimalarial activity - some chloroquine-resistant malaria strains are still vulnerable to quinine - and I can't find any information about whether their antiviral activity is the same. They're two pretty different molecules and I don't think it's fair to say that anything that works for one will also work for the other. Even if they do work, I don't know how to convert doses. It looks like the usual quinine dose for malaria is about three times the usual chloroquine dose, but I have no idea how that translates to antiviral properties.

Second, I don't know how much actual quinine is in cinchona. Quinine is a pretty dangerous substance, so the fact that the FDA doesn't care if people sell cinchona makes me think there isn't much in it. This paper suggests 6 mg quinine per gram of bark, though it's using literal bark and not the purified bark product they sell in supplement stores. At that rate, using this as an example cinchona preparation and naively assuming that quinine dose = chloroquine dose, the dose corresponding to the Chinese studies would be 160 cinchona pills, twice a day, for ten days - a level at which some other alkaloid in cinchona bark could potentially kill you.

Also, reverse-quarantining doesn't just benefit you, it also benefits the people who you might infect if you get the disease, and the person whose hospital bed you might be taking if you get the disease. I don't know what these numbers are but they should probably figure into your calculation.

Model estimating the number of infected persons in the bay area

I tried to answer the same question here and got very different numbers - somewhere between 500 and 2000 cases now.

I can't see your images or your spreadsheet, so I can't tell exactly where we diverged. One possible issue is that AFAIK most people start showing symptoms after 5 days. 14 days is the preferred quarantine period because it's almost the maximum amount of time the disease can incubate asymptomatically; the average is much lower.

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