Questions on the coronavirus

The following questions are actual questions, I have no agenda on this issue:

1. We are told that the public should not buy masks as they are ineffective, and also that the widespread purchasing of masks will create a shortage for health care workers.

Why is it so essential for health care workers to wear ineffective masks?

2. We are told that the public should not buy masks as they are ineffective. Rather, the most effective things to do are to stop touching your face and wash your hands frequently.

But if I wanted to stop touching my face, I’d wear a mask. Otherwise I might touch my mouth or nose without thinking.

3. We are told that viruses like cold and flu are much worse in the winter and become less widespread in warm weather.  But we are also told that virus transmission usually occurs in enclosed spaces like airplanes, schools, workplaces, cocktail parties, movie theaters, etc.  In developed countries like America we have heat in the winter and air conditioning in the summer.  So why does time of year make such a big difference?  ( I have no doubt it does make a difference.)

We are told that the coronavirus might become much less severe as it warms up, or might not decrease in intensity.  We’ll have to wait and see.  But why?  Surely there are many tropical parts of the world that are always warm.  How is the virus progressing in those regions right now?

When I look at the map, it seems like there aren’t many tropical cases outside Singapore, which of course has lots of air conditioned spaces.  Is this fact relevant?  You can argue that the infection data is undercounted in the tropics, but the more accurate fatality data shows the same pattern.  No deaths in Africa, South America, and India, and only two in Southeast Asia.  Northeast Asia has dozens of deaths.  Is that a hopeful sign for the summer, or not?

PS.  This caught my eye:

It seems like the Diamond Princess is the only “country” where we have a fairly comprehensive testing of the population.  If we assume that cruise passengers skew a bit toward the elderly, does this suggest an actual death rate of about 0.5%?

PS.  This caught my eye:

China prepared to evacuate its citizens from overseas areas with serious outbreaks, foreign ministry says



60 Responses to “Questions on the coronavirus”

  1. Gravatar of AL AL
    1. March 2020 at 10:41

    I believe the thinking on warm weather is not that the actual temperature makes it harder for the virus to spread.

    Rather, in summer, daylight is longer and stronger, so UV radiation is helping to sterilize surfaces and atmospheres. Windows are open, and people tend to spend more time outdoors, so they’re not in close contact in sealed spaces sharing recycled air. The air is more humid, which impacts virus’ abilities to take root in people’s nasal passages and sinuses.

    These are some of the reasons cold and flu outbreaks are less common in summer.

  2. Gravatar of David R. Henderson David R. Henderson
    1. March 2020 at 10:59


  3. Gravatar of ssumner ssumner
    1. March 2020 at 11:00

    Thanks Al.

    Thanks David.

  4. Gravatar of Ray Lopez Ray Lopez
    1. March 2020 at 11:29

    Excellent!! I will answer the questions of Glaucon, I mean, Sumner.

    1., 2.: Masks just keep the infected from infecting, so Sumner makes a good point. I think masks for hospital workers are just a slight extra precaution. PS–it’s common for the non-infected in Asia to wear masks, even in healthy times, they are almost a fashion accessory.

    3. Viruses diminish in summer. Two points, first, the common cold throat virus, ‘rhinovirus’, are temperature sensitive, hence, they take over cells during cold weather, thus wearing a scarf around the throat is effective to stop them (last 10 years research), so maybe the SARS/nCOv-2019 virus is the same, but in general, poster Al above is right, sunshine is the best disinfectant. However, probably Africa and India just don’t have the testing kit to detect the Covid-19 virus.

    4. Diamond Princess (DP) may be ideal in that it became a ‘floating hospital’ where the cruise ship owners had a powerful incentive to keep infected oldsters alive, to avoid the inevitable class action lawsuit damages. Covid-19 liquefies your organs so arguably keeping DP victims alive for a year and a day (the usual tort limit in the USA) after they debark is what’s driving the owners to providing the best health care for DP victims. If the DP victims die after that, it’s “out of sight, out of mind” and during litigation it will be argued they died of natural causes, mitigating damages. In the real world, victims won’t be given such superior attention.

    In conclusion, Sumner did well to highlight the commonplace but flawed nature of today’s medical advice. I could write a column on this too. For example, you’re told to exercise, avoid red meat, don’t smoke, and you’ll avoid cancer, but the cancer wards are full of fit young people who don’t have a genetic predisposition to cancer. You’re told in Asia to wash your hands, practice basic hygiene, to avoid Ascaris lumbricoides (giant roundworm) but a doctor I talked to says he does all that and every so often he gets the worm, so he takes as a precaution a de-worming pill once a year. I too got the worm, it was asymptomatic, about 12 inches long, and quite a shock to see it squirming in the bowl when I returned to the States. When I fished it out and showed it to the doctor, they freaked a bit and said it was the first time they’d seen this outside of a textbook (common though in SE Asia).

    You’re welcome! (Do I get a “Thanks Ray”?)

  5. Gravatar of Christian List Christian List
    1. March 2020 at 11:32

    About the weather: the theory seems to be that the droplets that carry the virus do not stay suspended in hot (or humid) air as long, and that the warmer temperatures lead to more rapid virus degradation. That’s the theory, but since it’s a new pathogen we must simply wait and see.

    About the masks:

    Your eyes are not protected, if you receive droplets, the pathogen goes over your eyes.

    The filters of the masks only last a few minutes (about 15-30min), then they leak because of your humid breathing air, then you have to hang them up to dry. This is ideal for hospital staff who go into the isolation rooms for a short time and then come out again. For normal people it is useless.

    That’s the official version, the semi-official version is of course that all the hoarding done by average people is extremely damaging:

    Hospitals around the world desperately need masks, but they’re not getting enough. It’s not that we doctors are afraid of the virus — I personally don’t wear any masks — but the disease can last 2-6 weeks plus possible quarantine, so it’s kind of catastrophic if masses of hospital staff become sick and are then lost for weeks in this critical time.

    Addendum: Sick people who wear masks are not a bad idea, because they reduce the viral load in the ambient air. Of course they should only wear them when they go outside, which they shouldn’t do in the first place. For healthy people, masks do little to nothing, except that they take away all the masks from the hospitals.

  6. Gravatar of P Burgos P Burgos
    1. March 2020 at 11:37

    How warm has it been in Guangdong province over the past couple of months? The WHO seemed impressed at the scale of coronavirus testing there (300,000 people tested, Bruce Aylward claimed) and said that they don’t think that China had missed many cases. I calculated the case fatality rate for the province the other day, and was about .55% so far.

  7. Gravatar of Becky Hargrove Becky Hargrove
    1. March 2020 at 11:44

    I calculated the benefit of a mask for the same reason, as a reminder not to absentmindedly touch my face after possibly touching a surface or product containing the virus. If need be I think scarves might serve the same purpose. Plus they could probably be washed outside in hot water and soap, before bringing them back into the house.

  8. Gravatar of P Burgos P Burgos
    1. March 2020 at 11:45

    Also, I would be a bit circumspect about the fatality rate in places where medical resources are not overwhelmed by the virus. China has only managed to keep the infection from spreading like in Hubei by shutting down the entire country for about 6 weeks or so. And China has not given an accounting of how many people without coronavirus have died in Hubei due to a lack of medical care. It may not even be possible to figure that out right now. What would really be encouraging would be if China is able to go back to work without the number of cases exploding.

  9. Gravatar of Christian List Christian List
    1. March 2020 at 11:46

    @P Burgos
    I assume air humidity is also important. When the air is already saturated, you can’t add many drops that can stay there for a long time. The winter in Western countries often looks like this: Dry air outside and inside, the heaters are on, the air is too dry. In addition, people may be closer together, you’re just more indoors. Ideal conditions for droplet and smear infections.

  10. Gravatar of Christian List Christian List
    1. March 2020 at 11:55

    One can at least state now that Scott’s (in)famous hypothesis that China was the worst possible place for the coronavirus to hit is now really being tested.

    I have no agenda, but I am curious about the outcome. In my view, Iran might already be well behind China. Let’s wait for the final results, the pandemic has only just begun.

  11. Gravatar of ssumner ssumner
    1. March 2020 at 12:46

    Christian, If that’s the answer, then things are even worse than I thought. I’ll just avoid getting advice from “experts” from now on.

    I’m only in places where I might catch coronavirus for maybe 10 minutes every two weeks. Otherwise I’m at zero risk, all by myself. So telling me “don’t wear a mask because it only protects you for 10 minutes” is kind of stupid. I’m not sure I’ll ever wear a mask, it’s just that this advice is very misleading.

    Burgos, Your estimate is interesting, close to mine. I believe Guangdong is cool but not cold during the winter, but am not sure.

  12. Gravatar of Michael Rulle Michael Rulle
    1. March 2020 at 12:52

    Interesting point on DIamond Princess. As mentioned in a previous comment, when an area the size of Nebraska has 70,000,000 people and 77,000 cases and 2800 deaths——is compared with 2017/2018 in US where 320,000,000 people had 42,000,000 cases and 61000 deaths (granted, full season versus partial but still higher ratios) all I can think of is 1) unknown % of tested 2) False positives 3)false negatives. 4)And numbers indistinguishable from random.

    What seems certain is we have not seen this specific brand of flu. With no vaccine. But vaccines are misunderstood in how they work. To quote CDC

    “It is not possible to predict how well the vaccine and circulating strains will be matched in advance of the influenza season, nor is it possible to predict how this match may affect vaccine effectiveness.“

    There are many random variables at work. We know it is not like Ebola and we know it is not “nothing”. So far this looks like a normal flu season. The question is whether it is sensible to treat it as such. Two months ago? No. Now, yes.

  13. Gravatar of aram aram
    1. March 2020 at 13:01

    These explanations for the masks (for SARS, though) seem pretty clear.

    Christian’s points are also good.
    Why would that make you skeptical of experts? Yes, you a non-doctor might theoretically benefit from a mask, but on average you won’t, except indirectly by reminding people not to shake your hand.

  14. Gravatar of Christian List Christian List
    1. March 2020 at 13:26


    you got the information now. I’m not telling you what to do with it. 10 mins is fine for the mask. What are you doing with your eyes btw? Are you wearing safety goggles? And don’t forget the special protection suit. Mask, suit, goggles, gloves — it looks a little weird at the gas station and the supermarket though.

    And another piece of information: the attack rate of the virus is estimated by virologists at 60-70% right now. This means that 60-70% of the population will get the virus one way or the other. The quarantine and protection measures currently have only two goals: to delay the pandemic so that it can be spread over a longer period of time. And protection of medical staff so that the really sick can still be treated.

    No time for scaredy-cats, scaremongers, selfish people, and anti-social hoarders, who aren’t even sick in the first place.

    Michael Rulle,

    you still didn’t understand that it’s not influenza. Therefore, your endless comparisons with “the flu” are not that helpful. You have also talked about H1N1, that supposedly was a new type (out of four) according to you. In reality H1N1 is simply type A, the most common type of influenza there is. Corona on the other hand is not “the flu”, it has nothing to do with influenza. You can compare apples and oranges as long as you want, at the end of the day influenza is still an apple, and covid-19 is a new kind of orange, unlike most other things we’ve seen before.

  15. Gravatar of Matt Matt
    1. March 2020 at 13:33

    There are still likely going to be several more deaths on the Diamond Princess – over the next week or so we should have a more accurate count of the number of deaths.

  16. Gravatar of Christian List Christian List
    1. March 2020 at 14:01

    This virus can really break Trump’s neck in several ways, and more likely than most attacks we’ve seen before. Interesting times.

  17. Gravatar of Anonymous Anonymous
    1. March 2020 at 14:36

    1. There are 2 types of masks: Surgeon’s Masks and N95 masks. The former give little protection to the wearer but protect others from droplets from coughing (which is why surgeon’s wear them). The latter give good temporary if used correctly: They have to seal properly and the wearer has to be careful to properly disinfect one’s hands before putting them on and not accidentally break the seal or infect oneself while touching the mask or while putting it back on after removing it to eat, drink, etc. Having worn them during the CA fires they are also quite uncomfortable. Would they offer some protection if one knows how to wear them? Yes, probably. So ignoring supplies it’s purely a tradeoff between risk of infection when not wearing one vs. infection from wearing one. And then of course it’s a triage situation where health care workers and similar frontline personal have a much higher chance of contact and infection and protecting them (and preventing them from spreading it) is highest leverage.

    2. Agreed. I think a cheap mask or scarf is a good idea and that advice is probably bad. One thing I like/have been trying: Wear disposable gloves purely as a reminder not to touch the face. They obviously don’t give protection (since they’ll get contaminated quickly) but can be useful for that. Also practice not touching it at home to cement the habit.

    3. I’m too lazy to find the thread right now but one expert I read speculated (I really should find the thread later) that it seems to last on surfaces longer than other coronaviruses (i.e. multiple days to more than a week) and that there’s reason to believe that higher humidity (and potentially temperate) lowers that time. But still very unclear.

    Hope this helps, I’ve been spending way too much time reading up on this.

  18. Gravatar of Ray Lopez Ray Lopez
    1. March 2020 at 14:40

    I think Dr. Christian List (LOL, Dr) may be a bit too pessimistic. While I do believe the stock market will crash so that the DJ-30 ends up at year 1999 levels (10k), I also think Covid-19 will be akin to the common flu in actual practice (not medically but in actual impact).
    See more here (note the optimistic scenario):

  19. Gravatar of Luis Pedro Coelho Luis Pedro Coelho
    1. March 2020 at 14:48

    1. Masks are effective if worn properly. As healthcare workers are much more likely to be in close contact with sick people, it is much more important for them. For most people, though, the overall risk is low and they will get it from close contacts around whom they don’t wear a mask. Finally, most people wear the masks wrong. IMHO, this should be the message: please take on a tiny risk so that healthcare workers at much higher risk can be protected. If you are, for some reason, at a high risk, here is how to wear one properly.

    Instead, authorities are lying to people (at best, muddling the issue). Also, asking for masks for healthcare workers would involve admitting they screwed up in not being prepared (why is there no “strategic mask reserve”? Not joking, why isn’t there one in most countries?).

    3. We don’t actually know.

    On the PS: the Diamond Princess mortality is not yet established. Unfortunately, some of the individuals are still at risk. It was at close to 1% last time I checked (7/705 or something). I’ve been seeing this case brought up since the mortality was 0.2%, but from infection to death takes 2-4 weeks, so the final numbers are still to be known.

  20. Gravatar of Luis Pedro Coelho Luis Pedro Coelho
    1. March 2020 at 14:56

    1. In “defense” of public health officials, they sometimes are so wrapped in an utilitarian/authoritarian way of thinking that they forget that other people might not understand that when they say “masks are not effective” it’s a cost/benefit statement about whether it is a good idea for authorities to recommend/mandate widespread mask usage rather than a statement about whether wearing a mask confers protection to the individual wearing them.

  21. Gravatar of ssumner ssumner
    1. March 2020 at 15:11

    aram, Just to be clear, I’m not claiming masks are a good idea for the public. But nothing Christian told me suggests that they are ineffective in reducing one’s chance of getting Covid-19. Your link is about SARS, a very different illness.

    Christian, Your usual idiotic comment. I don’t wear masks, except when working in extremely dusty areas (as I have asthma.) And I don’t recommend them. But if I did want to minimize my chance of getting the disease, to be one of the 30% or 40% who do not, I’d wear a mask on the rare occasions when I’m around other people.

    BTW, if 2/3rds of Americans get the disease, as you predict, that’s 200 million people, perhaps a million deaths. Is that your prediction?

    Anonymous, regarding the shortage of masks, I guess we shouldn’t have expected the government to see this coming. I mean no one was predicting a pandemic, right?

    Luis, Very good comment.

  22. Gravatar of Christian List Christian List
    1. March 2020 at 15:34

    I’m pessimistic? You predict that stock markets will plummet to their 1999 levels.

    I don’t see how that could happen at all, not even 2008 levels, but let’s see if you are right. I assume there will be a rather small setback, maybe 1-3 years will be lost and then a fast recovery, nothing more.

    But I hope you’re right, I’ve been waiting years for a big setback, but Scott has always been correct so far and I don’t see why he should be wrong this time.

    Apart from the stock markets, I agree with you and the article you linked to. The article is informative and accurate. There’s not much to worry about, it’s just a bit unknown territory right now, nothing more.

    @Luis Pedro Coelho
    Good points, all of them.

    The issue with the masks is in part poor communication indeed. But one must also admit: no matter what the officials, doctors and politicians say, a few people will always run to the pharmacies, supermarkets and DIY stores and buy all the masks.

    Tuesday was the first big day of the outbreak in Germany. I met the biggest pharmacist of our town in the evening and he told me that he never experienced such a day in his 50 years of service. After 1.5 hours all masks, gloves and disinfectants were sold out.

    I advised him to simply increase the prices by a factor of ten, 100 or 1000. Why does nobody do that? That would be the economically correct answer, but the politicians and salesmen are afraid of doing it.

    In the region of Genoa a very old man stood in shock in front of empty pasta shelves and said something along the lines of how: People today are crazy, we weren’t even this panicked back in the days when WW2 broke out.

    strategic mask reserve

    Hospitals built up stocks 1-2 months ago, but in a pandemic like this any stock is ultimately too small.

    Scott won’t like to hear this, but I think sales bans and rationing are more effective when masks are really scarce. The manufacturers don’t raise prices adequately, they don’t want to present themselves as
    “extortionists”, so sales bans won’t even limit the production, maybe even on the contrary because the state guarantees large purchase quantities and prices above normal.

  23. Gravatar of Benjamin Cole Benjamin Cole
    1. March 2020 at 15:43

    The widely varying reported death rates from coronavirus are what puzzles me. My hunch is there are a lot of people who never report to a doctor as they have a mild case or even a symptomatic. Ergo, the coronavirus scare is overblown.

    China is a nation with 1.4 billion people and it looks like they’ll have several thousand deaths from coronavirus. It may actually go on for a number of years, perhaps they’ll have 10,000 or 20,000 deaths.

    In the US, that would translate to about one-quarter as many deaths, or say 5,000 deaths.

    I am not making light of anyone’s death, on the other hand these sort of numbers are swamped by deaths from other causes.

  24. Gravatar of Anonymous Anonymous
    1. March 2020 at 15:57

    Scott, Yeah…. I read that e.g. New York State has a huge warehouse of such supplies but reading the excellent article linked below there do seem to be more shortages than I realized – I thought this was mainly a general warning. At least one quote makes it sound like the issue is mainly about longterm supplies and that they are working on building a stockpile but there’s a lot of medical stuff and the masks don’t last very long (multiple hours from my knowledge btw, I forgot to mention that above).

    In terms of numbers the problem is that ~20% get quite seriously sick (and I again forget the number because I’ve been bad at taking notes today) some significant share of those need hospital treatment or even ICU bed. The fatality rate estimates generally assume that level of care and can rise dramatically AFAIK if that’s not available. Given the tiny spare capacity of the US health care system this is going to be quite a problem and one of the reasons it’s so important to spread out the cases as much as possible. There also seems to be be serious lung damage and potentially other effects on a reasonable percentage of the serious cases that survive which is a very scary fact I haven’t seen mentioned very often (so hopefully I’m wrong!).

    Small outbreaks are easier to track and contain and it’s really unfortunate that we have at least 1 large outbreak in Washington, a likely large one in the Bay Area, and I’m not sure on the size of Oregon’s. Meanwhile apparently NY has tested 8 people and doctors have not been able to test suspected serious cases (I’m hoping this is out of date now).

    Finally, it seems like we need to focus on testing all hospital patients with strong symptoms in Washington, California, and Oregon as soon as possible and generally test other potential cases in those areas as well as ramping up testing of such patients all across the US (maybe big metro areas first?) to get a sense of where else this may be happening.

    Ok, one more: I saw a reasonable suggestion from some expert (again don’t have the source off the top of my head) that we need to reallocate resources from checking healthy travelers from various regions to focusing on tracking down these local spreads

  25. Gravatar of Anonymous Anonymous
    1. March 2020 at 16:05

    Benjamin Cole, could you show how you derived those numbers, they seem extremely low. I saw the high numbers from a Harvard Epidemiologist (40-70% unless we take very extreme actin & get lucky) which I’m hoping are wrong but looking at reported growth times it’s 1 week until the number of infections doubles so that grows very quickly. At 10% of the population that’s 660k deaths, but there’s no way our medical system can handle anywhere near those numbers of severe patients (6M severe cases) so the rate would be higher.

    At those doubling rates we’ll have 16x the patients in a month, 256x in two months, and 4k in three months. I’ve seen estimates for Washington of a few hundred to about a thousand suspected infections so that get’s us to high numbers quickly.

    Once we start seeing those numbers (even 10-20x) I’d think people start taking much heavier precautions but the disruption of that would obviously be massive.

  26. Gravatar of Christian List Christian List
    1. March 2020 at 16:11

    But if I did want to minimize my chance of getting the disease, to be one of the 30% or 40% who do not, I’d wear a mask on the rare occasions when I’m around other people.


    you are a bit dense here. If you really want to reduce your risk relevantly, then you must either give the mask to the covid-19 patient who is currently coughing on you. Or you must do what the medical staff does: full gear with glasses, suit, gloves and mask. A mask alone does not reduce your risk in a relevant way, let alone “minimize” it.

    BTW, if 2/3rds of Americans get the disease, as you predict, that’s 200 million people, perhaps a million deaths. Is that your prediction?

    I don’t make predictions like this, we don’t even know the mortality rate in America yet, you can only say that retrospectively for sure, maybe in a few weeks.

    I only stated the attack rate that leading virologists currently suspect. That does not necessarily mean attack rate per year btw, an attack rate can be extended over two or maybe even three years if we are lucky.

    So yes, there could be over a hundred thousand deaths per year for about 2-3 years. That would be similar to a severe influenza outbreak, but 2-3 years in a row, and with twice as many casualties each year.

    This is the worst case scenario I’m looking at right now. Children almost unaffected, thank God. Many deaths over 80 years old. But one can also die from it in individual cases as a teen or tween if one is very unlucky (as with influenza).

    Trump underestimates the danger, tries to whitewash everything. That and the collapsing economy (without sufficient Fed reaction) could really cost him his job.

    If you really have severe asthma, you are naturally more at risk. I agree with you there. No hard feelings. Good night, and good luck.

  27. Gravatar of ssumner ssumner
    1. March 2020 at 16:32

    Christian, You said:

    “A mask alone does not reduce your risk in a relevant way”

    You’ve given me zero reason to believe this.

  28. Gravatar of ssumner ssumner
    1. March 2020 at 16:38

    Anonymous, Good points.

  29. Gravatar of Anonymous Anonymous
    1. March 2020 at 16:58

    I only saw one other mention of n95 masks here, but these are what the CDC recommended for healthcare workers and much more effective than surgical masks (

    I don’t work in healthcare but apparently healthcare workers receive special training to learn how to fit them on properly, and so they aren’t as effective for the general public.

  30. Gravatar of Christian List Christian List
    1. March 2020 at 17:23


    okay I’ll meet you halfway here. One can make up some sort of conspiracy theory that the authorities want the masks for the hospital staff and therefore understate the benefits. That may be even true. One argument against this theory would be that the hospital staff doesn’t wear suits and glasses for fun.

    It’s best to use an N95 respirator, as it’s called in the US, but these masks are difficult to wear. I’m trained for this and I won’t wear these masks unless Ebola breaks out. They are very uncomfortable, breathing becomes really hard, it’s wet, it’s hot, it’s no fun at all, and if you are not trained, you will breathe wrong, out to the sides, because it is so relieving, but then the mask does not work as intended.

    At least the masks don’t increase the risk, that’s true, unless you behave more risky because ot the mask, in a false sense of security — but that’s exactly what happens quite often. People do something risky and put on their masks because they think they are better protected, when in reality it would be better to really reconsider the risky behaviour in the first place.

  31. Gravatar of mbka mbka
    1. March 2020 at 17:54


    I’d have to agree with most of what Christian List said (hard to believe I just wrote this!). That said, on masks: common sense suggests that an additional barrier, even if only partially effective, will reduce your risk. At least some of the droplets will be caught etc. But it may also lead to complacency, so who knows. Might be really zero effect.

    In the big picture, it’s about reducing the transmission rate below 1, so each and any reductions are welcome, even though not perfect. But Christian is absolutely right, person coughing in your eyes and the whole mask thing is useless. Pizza guy coughing on your pizza before delivery. And what have you. Masks work for hospital workers because they change them often, wear goggles and gloves too, and are in constant, very close contact with coughing people which often need to be intubated. Look at it as a matter of statistics. In hospital, crucial. In normal life, very little effect.

    A few random remarks that haven’t been made yet:

    – why summer / winter: a study in the early 2000’s noted that flu viruses (different virus of course) tend to stay suspended in the air much longer in dry cold air. In humid air, they become a condensation nucleus and form a droplet. Once again, this doesn’t mean zero infection rates, but it incrementally contributes to lowering the transmission below 1 (each sick person transmitting on average to less than one additional person).
    – effectiveness of measures. Tales from Singapore: masks were sold out in milliseconds weeks ago. Then toilet paper was off the shelves, Lysol spray, and hand sanitizers. Right now, you can buy these items again, hand sanitizer was the last to return to the shelves. Then government gave out 4 masks per family. Purpose: to wear ONLY when you’re sick on the way to the doctor. I estimate about 1% of the public wears masks on the street (tourists??). But all buildings, even some malls, have mandatory temperature checks, and of course there are quarantaines for the affected. But less than you may think – currently 300-odd are in quarantaine for pop 5.5 Mio. Very many offices have split work from home arrangements now, meaning that half the team works from home, half is in the office. Purpose: so only half of a working unit gets sick/quarantained at any one time. And of course again it lowers human density, and hence, transmission rates.
    – the rules for quarantaine orders seem to be about length of contact. We are told the key number to look out for it is 30 min or longer contact with an infected person that is routinely within 6 ft or less distance. And if you look at infection clusters, they’re all about same office, same family. Very few picked it up at the mall or the elevator. But within a family, almost all will get it, similar for offices. (Singapore experience)
    – with these measures in place, meaning, contact tracing, quarantaines, and split team work from home in larger organisations (for sure not the SMEs that employ most people here), Singapore adds cases on a more or less linear basis this past month. Random 1-4 new cases per day and it’s more or less a linear curve. Not exponential.
    – Streets and malls had a drop of 50 to 90% traffic for the past 3 weeks. Then, this weekend, pandemonium: as if everybody and their sister were sick and tired of being afraid, everyone went out, you couldn’t get a seat at a restaurant, traffic jams galore, beach promenade was bursting. So if that’s a sign of how long economic panic lingers, I’d be optimistic.
    – Tropical countries: as with SARS, those tropical humid countries that are poor and without a/c seem to be generically less affected. So yes, dry air, hot or cold, mixed with high population density (either generally, or because people cluster indoors). Iran of course is both cold in winter and has dry desert air, often high altitude. The summer doesn’t kill the virus but generally, less human density because more outdoors / windows open, and more humidity, work to lower the transmission rate below 1. And that’s all you need to happen.

  32. Gravatar of Anonymous Anonymous
    1. March 2020 at 18:44

    mbka, Thanks for that, very interesting. Some of this seems driven by the low case count though, no? The chance of catching it elsewhere seems like it could be far higher in places where more people have it.

  33. Gravatar of Steve Steve
    1. March 2020 at 19:48

    The difference between summer vs winter is overstated. A virus needs to find a new host roughly once a week, or it is kaput. In the winter, influenza succeeds in finding 1.25 new hosts, so it grows exponentially until March. In the summer, influenza only finds 0.80 new hosts, so it receeds exponentially. Coronavirus is finding 2.0 to 3.0 news hosts, so it is also growing exponentially.

    Singapore and China are poor examples. Singapore has performed extremely rigorous case by case tracking and contact isolation. China implemented a military lockdown. The USA is following Iran’s example and will have Iran’s outcome. The virus is hitting colder areas first because it is following Silk Road trade routes. History repeats.

  34. Gravatar of Anthony C Vicari Anthony C Vicari
    1. March 2020 at 20:09

    For (3): This is at least in part about humidity. Viruses enter the air enclosed in liquids (from sneezes, coughs, etc.). When air has very low relative humidity, the moisture forms smaller droplets, which stay in the air longer b/c they are lighter. Hence the equilibrium density of viruses in the air is higher even if they enter the air at the same rate. Heating raises temperature without adding moisture, lowering the relative humidity of indoor air in winter. Summer has the opposite effect, but less so because air conditioners do remove moisture from the air as they cool.

  35. Gravatar of mbka mbka
    1. March 2020 at 20:15


    SG was one of the first countries with imported cases. Now it’s about 100 cases for pop 5.5 Mio, current cases all locally transmitted. You can do the math: That’s as if Korea, pop 50 Mio, or France for that matter, had 1000 cases. Or China, pop 1,400 Mio, had 25,000. Or the US 5,000. In other words, once you adjust for population, the case load in Singapore is lower than China or Korea, but just by a factor of 2 or 3. However, as always, what matters is the growth rate. Is growth exponential, linear, or on the decline? That’s really what one should look for. So I take the linear increase, rather than exponential, as a good sign.

  36. Gravatar of mbka mbka
    1. March 2020 at 20:25


    China and Singapore are quite good examples. The lockdown only applied to Wuhan / Hubei, but plenty of cases were exported to other cities and regions. Yet, it seems to be stabilizing in all of China. And Singapore is doing things that are perfectly within reach of other developed countries. Key in Singapore was, to do it early. Korea did not, and we can see the results. Italy was completely caught off guard. Singapore’s measures were far, far lighter than Korea’s, Italy’s, or China’s (locking down entire towns).

  37. Gravatar of Steve Steve
    1. March 2020 at 20:28


    Viruses are always and everywhere exponential in behavior.

    The trick is that humans and viruses inevitably engage in a dance toward an exponent of 1.0. Virality, immunity, seasonality, and social distance are the only factors determining whether the exponent is temporarily above or below 1.0.

  38. Gravatar of mbka mbka
    1. March 2020 at 20:47

    Steve, I think we’re talking past each other. In this context, what interests me is the growth curve of human cases, not the academic definition of the growth formula. So forgive me if I use a phenomenological vocabulary. Besides, ecologically speaking, in a real population you’d actually expect logistic growth, not exponential. That’s because besides the factors you mentioned there is also a limited population to infect (carrying capacity). So what you get is first exponential-looking, then roughly linear looking, then plateauing. Like what happens in China already.

  39. Gravatar of Steve Steve
    1. March 2020 at 20:57


    The carrying capacity is 8 billion. We are orders of magnitude away from the logistic coming into play.

    I do realize that both exponential and logistic are approximations; in practice a graph would be a better model, where the virus explodes into a small new pocket, then temporarily slows down. But that is factored into the “social distance” included in my parameterization.

  40. Gravatar of mbka mbka
    2. March 2020 at 00:54


    the curve shape in China did follow a logistic (discounting the mess-up in the middle on 2/12 when they changed the definition of a “case”):

    The very fact that it does seem to follow a logistic in China, that quickly, even though only 1 province had been locked down, gives me hope. My guess is that harmless variants are spreading unseen everywhere, immunizing enough people for herd immunity.

  41. Gravatar of Ray Lopez Ray Lopez
    2. March 2020 at 02:10

    @ (Dr) Christian List – don’t argue too much with Sumner, he’s like a Global Warming denier, I mean, the man is rigid in his thinking. Just once in his many years if blogging did I read him say “Let’s suppose money is neutral”. Just once. I myself think a better patent system would boost Total Factor Productivity and usher in a Magic Kingdom of innovation, but even I say, based on history, patents may not matter (depends on the elasticity of innovation, which is hard to measure and test for).

    As for your “ban mask hoarding” as a solution, I agree. Bans, as in bans on plastic bags, work. Speaking as a libertarian. In fact, in economics what’s known as ‘wartime communism’ works: a top-down ‘command-and-control’ economy works to efficiently direct output in times of distress (the Visible Hand works in the short-term). Something libertarian Sumner and his Hoover Inst pals won’t acknowledge, anymore than they’ll not acknowledge Adam Smith’s “Division of Labor” leads to imperfect monopolistic competition. Off-topic, Alexander Hamilton was right on this point.

    Catch you later, and watch for the panic buying points of DJ-30 at 20k then 10k (buy at both levels).

  42. Gravatar of Ray Lopez Ray Lopez
    2. March 2020 at 02:40

    @myself – sorry, in my post above I forgot to mention Georg Friedrich List (6 August 1789 – 30 November 1846) in the same breath as Alexander Hamilton, an example of Great Minds thinking alike, and of the phenomena of simultaneous invention of an idea (sometimes used to justify not granting patents, but I digress).

  43. Gravatar of Benjamin Cole Benjamin Cole
    2. March 2020 at 02:55

    1. March 2020 at 16:05—-

    Okay, it looks like China is reporting about 500 new cases a day. Let’s say that jumps up to 1,000 a day as people return to work.

    Let’s assume a 1% fatality rate.

    Okay, so 10 people a day start to die from coronavirus in China, over the longer run, or about 3,500 to 4,000 a year. Remember, this is a nation with 1.4 billion people.

    Let’s say I am off, and 7,000 to 8,000 die per year. It is not that bad (in the scale of China).

    I am not making light of any death. But most people who are dying are old. The economic impact could be limited—-the panic could be real, in any city or nation that sees a surge in cases.

    Maybe coronavirus is different, but with other viruses, as people become infected, and recover (many are asymtpomatic) they become barriers to fresh infections.

  44. Gravatar of Matthias Goergens Matthias Goergens
    2. March 2020 at 03:35


    Resident of Singapore here.

    I don’t know what the actual mechanism is that makes the (new) corona-virus less dangerous in summer. But older strains of corona-virus are some of the microbes that can cause the common cold. And the common cold naturally goes around during ‘flu season’ and tends to be less prevalent at other times.

    So the experts probably expect whatever mechanisms causes common cold to wax and wane seasonally to apply here. (Weirdly enough, we also have flu seasons in Singapore, even though we don’t really have seasons.)

    In general, it’s not just temperature, but also humidity: if it’s cold outside and you heat indoors, the absolute humidity stays the same, but the relative humidity drops. When it’s naturally warm, then indoor humidity is the same as outdoor humidity.

    From personal observation: overly dry air is bad for your throat.

    Aircons, like they are common in Singapore, actively remove humidity. So Singapore indoor air has a reasonable relative humidity level; and a much lower absolute humidity than outdoor air.

    For once, I agree with what Ray Lopez wrote in his first comment.

  45. Gravatar of Matthias Goergens Matthias Goergens
    2. March 2020 at 03:49

    Scott, another thing: the absolute number of deaths to expect might be a bit misleading.

    People die all the time. What’s interesting is how many quality adjusted life years (QALY) are lost. The Spanish Flu killed lots of young people in their prime. So that’s horrible on a QALY measure.

    Most variants of the common cold and the flu inconvenience most people for a while. But old and weak people are at a bigger risk of death.

    A healthy person missing two weeks, is like 2 / 52 QALY (if you assume that having flu-like symptoms is as bad as being dead). An old or weak person might die perhaps five years earlier than otherwise. So they are missing on out perhaps 5 relative bad years, so perhaps 0.5 * 5 QALYs? (All numbers made up.)

    I think the bigger impact is via economics: China being shutdown lowers their real GDP by quite a lot this year. If the world economy becomes permanently less open, that’s an even bigger impact. Or a less than ideal Fed response might trigger a recession. (I’m not worried about a recession in China: their central bank seems to have less restraints on keeping the economy afloat. The main risk I see there is that they won’t let their currency drop as much as necessary, for geopolitical reasons.)

    Being killed outright is bad enough, but at some point GDP converts to QALYs.

  46. Gravatar of dtoh dtoh
    2. March 2020 at 05:23

    Can anyone explain Vietnam. Zero active cases.

  47. Gravatar of P Burgos P Burgos
    2. March 2020 at 05:35

    Does anyone know if smoking or respiratory damage due to air pollution contribute to the severity of cases in an outbreak or susceptibility to infection for this new virus? Do those things happen with other respiratory viruses? China has pretty high smoking rates and has had pretty bad air pollution for decades.

  48. Gravatar of Spencer Hall Spencer Hall
    2. March 2020 at 05:56

    A negative supply side shock is exactly what Dr. Scott Sumner says should be handled through an increase in N-gDp (without regard to a change in inflation).

    “A supply shock is an event that suddenly increases or decreases the supply of a commodity or service, or of commodities and services in general. This sudden change affects the equilibrium price of the good or service or the economy’s general price level.”

    “In the short run, an economy-wide negative supply shock will shift the aggregate supply curve leftward, decreasing the output and increasing the price level.” — Wikipedia

    Sumner: “Increased probability that monetary policymakers will not be aggressive enough to prevent a recession, and if the recession occurs then demand will still be rather sluggish in January 2023 because the Fed will be too hawkish in the recovery…In other words, we need adequate NGDP in 2023, and if we don’t get it then it will be the Fed’s fault.”

    Scott Sumner is exactly right.

    Dr. Nouriel Roubini is nearly correct.

    “If its output shrinks just 2 per cent in the first quarter, that is an annualised contraction of 8 per cent. A V-shaped rebound would therefore require the same annualised growth, which exceeds the 6 per cent that China managed before the virus”

    There becomes an elongated “sweet spot” in monetary flows, volume times transaction’s velocity , where inflation is interrupted for an increased period of time. The Fed should take this opportunity to ease its money policy. It should lower the remuneration rate on interbank demand deposits.

  49. Gravatar of foosion foosion
    2. March 2020 at 09:58

    The two common statistics are case fatality rate and mortality rate. Case fatality rate is the percentage of people with symptoms who die. On the Princess, they are testing everyone. Percentage tested who die is not the same as percentage who are symptomatic who die. The current estimate for CFR is around 2%, although it’s still a preliminary estimate. The CFR for the flu is usually listed at about 0.1%

    Mortality rate is the percentage of the population who die from the disease. This will obviously be a much lower number than the CFR.

    A major unknown is the transmission rate, making it hard to know how many are likely to get the disease.

    A concern about the US is that isolation/quarantine is harder to implement. Many people don’t have paid sick leave and can’t afford to take time off from work. Testing and hospitalization are beyond the financial means of many (no insurance, high deductibles or copay). Both of these issues are much less of a problem in much of the rest of the developed world.

  50. Gravatar of Michael Rulle Michael Rulle
    2. March 2020 at 10:14

    I read the story in the WAPO today by a man (from the Diamond Princess) who has the Virus and is still in quarantine. What struck me—-and it had not been obvious to me before—-is how long he has had the virus.

    I don’t know if he is typical. They are treating it like one would treat Influenza (Lots of liquids etc). Not knowing how long he had it, and like Influenza, symptoms happened suddenly—high fever, cough,etc.—even though—he discovered later he already had it —without symptoms.

    But tests indicated he caught the Virus while on the ship—so it appears he has had it for at least 17-20 days.

    As of now he “he does not require much medical care” and feels fine. He is still testing positive. He has to test negative 3 days in a row to be released. He is in his late 60s.

    I don’t know whether to interpret his story as good news or bad news—probably some of both. The bad news is he is a “Typhoid Mary” both before his symptoms as well as after his symptoms and for a long period of time.People who don’t know they have it (which seems like it should be a large number) will be transmitting it–at what rate?

    The “good news” is he seems like he will survive—-but also—it appears like he would have survived anyway—–We do know a lot of people get the Flu everyday—–and certainly very few are tested to see if they have this—-but if they do have this—-they 1) can transmit it for a longer period of time and 2) it may not be worse than flu

    -also do not know what protocols will be for “post death” testing on people who have died because of symptoms that look like the Flu–but it will take a long time for this to be sorted out—-I guess that is why so many died from the novel “flu” in 2001—-this is a “novel” corona which may have similar results.

  51. Gravatar of Michael Rulle Michael Rulle
    2. March 2020 at 10:16

    PS I meant “novel flu” of 2009

  52. Gravatar of Ray Lopez Ray Lopez
    2. March 2020 at 10:39

    @P Burgos – see, re smoking and Covid-19, this report:

    @Michael Rulle – was there a point to your boring long post other than showing your ignorance? Sorry, it’s probably better just to ignore you.

    @everybody – check – comment section, today’s date, for a rebuttal of Sumner’s thesis that AD does not go down much when Thanos snaps his fingers and half the planet dies. From JP Morgan Chase’s top economist.

  53. Gravatar of Joseph Joseph
    2. March 2020 at 12:17

    1. While masks may be ineffective specifically against coronavirus they are still important for normal health care usage.

  54. Gravatar of Cameron Blank Cameron Blank
    2. March 2020 at 12:52

    Nice example of what truly expansionary monetary policy looks like today.

    Equities up 3-4%, short rates down, long rates up, energy commodities up 5%, metals up 2%.

    This is mostly a US rally, with international equities up only about a 1%. It doesn’t seem like its related to the coronavirus seeming less bad, indeed news today makes it seem worse, but I’m not 100% certain of that. Seems to be mostly monetary policy.

  55. Gravatar of Don Geddis Don Geddis
    2. March 2020 at 13:05

    Sumner, I believe I can answer your “mask” question (albeit as a non-medical professional).

    The primary vector for virus infection is touching infected surfaces with your hand, and then touching your own mucus membranes (eyes, nose, mouth) with your own now-infected hands. The general public is mistaken to believe that a common transmission mechanism is to breathe in infected air.

    Healthy people wearing masks may actually have negative utility. Masks are hot, and uncomfortable, and itchy … so healthy people wind up touching their face with their hands more often when they wear a mask, and thus are more likely to get infected. The proper protocol for the healthy general public is to avoid touching others (no handshakes), to wash your hands regularly, and to try to stop touching your own face.

    The primary people who should wear masks, are those who are already infected. Masks are effective at preventing sick people from exporting their internal viruses (cough, sneeze) onto surfaces for others to later get sick.

    Health care workers are a special case. They know their environment is infected. It isn’t sufficient to “just” wear a mask. They need gloves, and hand washing. And they need intense, non-intuitive training to practice how to stop touching their own faces. With proper training, a mask can be a minor component of avoiding infectious disease in a hospital environment.

    But a normal healthy member of the public, without behavior training, just putting on a mask, is: (1) taking a limited supply away from health care workers; and (2) likely making their own risk of infection greater.

  56. Gravatar of ssumner ssumner
    2. March 2020 at 14:45

    Everyone, Thanks for the info. Mbka’s comments on Singapore were especially interesting.

  57. Gravatar of Myb6 Myb6
    2. March 2020 at 20:56

    I’d also like to express my thanks for all the info in this comment section. It’s entertaining that the comments section of my favourite monetary blog is where I ended up finding a good epidemiology q&a.

  58. Gravatar of Tom Brown Tom Brown
    5. March 2020 at 01:54

    This was interesting:

  59. Gravatar of Random thoughts on the pandemic – The Rabbit Hole Random thoughts on the pandemic - The Rabbit Hole
    28. April 2020 at 10:23

    […] But they should have started on March 1st. […]

  60. Gravatar of Trump supported lockdowns – The Economist Trump supported lockdowns – The Economist
    11. November 2020 at 13:12

    […] out of control), although it’s intriguing to speculate as to what would have happened if he had followed me in questioning the experts (skeptical) view on masks back in early March.  The actual issue in […]

Leave a Reply