Monday, April 27, 2020

Covid-19 Uncertainty: Be willing to say “We don’t know”


Like many people, I find myself distracted by the virus, as if infected by a different virus that makes me into a zombie that has to read the news. I find myself unable to stop reading about models and what the exit strategy will be for the “stay at home” orders in the US and elsewhere. Policies in Sweden, Taiwan, Korea, and elsewhere are all fascinating. I know many others are infected, too; friends tell me, and journalists write about it.

At the root of the problem is uncertainty, which is something I’m thinking a lot about in my research on pesticides, too. Though we now know a lot more about the Covid-19 virus (and doctors are better able to treat patients), there are many things we still don’t know. Most importantly, we don’t know what the world will look like after the pandemic passes, and when that will be.

Some people are able to just live with the knowledge that we don’t know. A friend wrote to a small group of us proposing a trip sometime next fall, and when I wrote back “I think it is going to be more than a year before we can travel freely, don't you?,” another friend wrote curtly, “Guessing game at this point.” Since he is a surgeon, I was about to write back, “Well, you must have some model in mind.” But then I realized he was right; it is pointless to speculate, and I just have to accept the uncertainty.

And there is a lot of uncertainty. While China, Taiwan and Korea have done a great job containing the virus, how long can they maintain their containment policies, including closed borders? Paradoxically, the chaos in the US and much of Europe, including the lack of preparation, slow reaction and lack of testing, may lead the US to develop a herd immunity that allows the US to come out of the epidemic earlier than areas that contained it better.

We don’t know whether a vaccine is possible; after all, we don’t have a vaccine for other coronaviruses. So it is possible that the only exit strategy for the virus is to keep the epidemic at a low level, so that it does not overwhelm the hospitals, until the population develops enough immunity that the virus does not spread very easily. This, essentially, is the Swedish path, where people are encouraged to keep social distance but there has been no stay at home order.

As doctors learn how to treat patients better, the death rate is declining, and may soon be lower than the death rate for the annual flu. But at this point, we don’t know, because we don’t really know how many asymptomatic cases there are, so we do not know the total number of cases, which is the denominator for the death rate (death rate = # dead/# infected). So while we currently think the US is a mess, and that Southern governors opening up their economy now seem irresponsible, the US and Sweden may turn out to be the better way to get out of this pandemic. We don't really know.

Some people are obsessed with knowing whether they have had the virus. A friend of mine told me of a group of co-workers who decided to get antibody tests (which are starting to be available here for $200-$260 (see one example here). The test checks your blood for antibodies to tell you whether you have had a Covid-19 infection and developed the antibodies. I asked why they wanted this test; they said they “just want to know.”

This is very odd, because though they think they will be liberated after a positive test (meaning they have antibodies for Covid-19), actually, their behavior should not change whether it is positive or negative. If they are negative, they still have to wear a mask and stay home. If they are positive, they assume that if they have Covid-19 antibodies, that they cannot be re-infected. They are probably right, but we don’t know this for sure. One study found low levels of antibodies in recovered patients, suggesting they may have only weak or no immunity. There have been a few anecdotal cases of apparent “re-infection,” and while it is more likely that their original infection just lingered (i.e. that when they were supposedly recovered and virus free, that they still had the infection), we can’t be sure. So to be cautious, they should still practice social distancing. Furthermore, it is not like they can suddenly go to the movies or to restaurants: they are all still closed, and few of their friends can go anyway.

In addition, there are serious doubts about the reliability of these serological tests. There are now only four tests approved by the US Food and Drug Administration (FDA), but 107 that are merely self-validated andpossibly fraudulent or unreliable. Those are the tests that are easily available, of course.

Even with a “reliable” test there is a problem, because most tests are only 95% reliable, meaning that they make a mistake 5% of the time. If I test positive, it is more likely that it is a false positive. In Missouri, it is very unlikely that any one person has had a case of Covid-19. When rates of infection for California came back at between 1.5 and 2.4 percent, experts thought these figures were much too high. Though a recent study suggests NewYork City may already have a 14 percent infection rate, experts are skeptical. Certainly, in the St Louis metropolitan area, where we have 2,720 cases as of yesterday, (0.1% of our area population, and 127 deaths), the chances of anyone being infected is very small.

The main problem with testing, however, is that it is interesting and important for epidemiological understanding of the epidemic, but is not very useful for the individual. Specifically, if a population’s infection rate is low, say 2%, then a test that is 95% accurate is not very helpful. If I test positive, I have roughly the same chance of being truly positive and of being a false-positive. Ninety-five percent accurate sounds good, but it is not if you are testing for something that is very rare. (To think with another example, since Yellow Fever is extremely rare in the US and few have antibodies for it, if I take a test that turns out positive for Yellow Fever antibodies, it is a lot more likely that the test is wrong than that I had or was exposed to Yellow Fever.)

Testing is key for public health purposes. We need tests to see who has the Covid-19 disease so we can be sure to isolate them and then contact all who have been in contact with them, so they can self-isolate. And for public health purposes, everyone should wear a mask to avoid infecting others in case they have the virus, and they have to wash their hands regularly and avoid crowds.

But if you are sick, it does not matter whether what you have is the flu or Covid-19; the treatment is the same. You are going to have to let your body’s immune system fight the infection, just like you do for any cold or flu. You need to protect others as though you are infected with Covid-19 (or any communicable disease): isolate yourself, avoid contact with others, wash your hands and keep your dishes and cups separate, etc. From my individual point of view, if I have a fever and shortness of breath, I have to just assume that I have the coronavirus. But people want to know, so they want to take the test.

Models are the most sophisticated ways we try to predict how the pandemic will unfold, and they help us think clearly. There are even peoplewho take a “wisdom of crowds” approach and use multiple models to estimate more accurately (sort of what 538.com does for political polls). One expert claims that as the pandemic has progressed, predictions have become more accurate, but that is a bit like saying that as you drive closer to your destination, your prediction of your arrival time is more accurate. By the time the pandemic is ending, we will not have much uncertainty. In the meantime, I'm willing to say, "I don't know."



Wednesday, April 01, 2020

The Science and Culture of (Medical) Masks


There have been reports the CDC is reconsidering its recommendation that people not wear a surgical mask when they go out (see WaPo story here and NY Times story here, for example). As it has become clear that asymptomatic people can transmit the coronavirus, more and more Americans have been wondering whether it would not be a good idea for ordinary people to wear masks all the time.

Scientists have long said that wearing surgical masks to protect against SARS and Covid-19 is not effective. The scientific view is that surgical masks help prevent someone who is infected from spreading the virus, but wearing a mask does not protect against becoming infected. (Here is an adamant position against non-sick people wearing masks, from 29 Feb.)  As this NPR story from 2015 notes, masks are good if you are sick so you don’t spread germs to others, but it is better to just stay home. The CDC, as of today, only recommends wearing a facemask around other people if you are sick, or if you are in the same room as someone with coronavirus who cannot wear the mask (e.g. because of difficulty breathing). 

The Hong Kong health authorities during SARS essentially agreed with this viewpoint, and said that people should wear masks to avoid stigmatizing anyone who had to wear a mask. The thinking was that if only sick people wear masks, then they would be discriminated against; people who should wear one would not do so to avoid being shunned.

Actually, most Hong Kong residents felt that wearing a mask would help at least a little, and even if they had doubts, “it’s better to be on the safe side” and “it can’t hurt.” It has gradually become common sense that wearing a mask protects the wearer. And this approach predominates with the coronavirus; the Hong Kong government encourages people to wear a mask when they go out. This is contrary to the WHO, which only recommends wearing a mask if caring for an infected person.

An opinion piece in the NY Times by the medical anthropologist Christos Lynteris argues that though there is little evidence that wearing a surgical mask is a good prophylactic against the coronavirus, in Asia wearing a mask is a sign of being modern, of taking hygiene seriously, and of concern for others because wearing it prevents the spread of the virus if the wearer is asymptomatic. Chinese first wore masks in 1910, when the Cambridge-educated doctor Wu Liande recommended the use of gauze masks to fight the pneumonic plague. He was right, and his success, in contrast to European doctors at the time who disagreed with him, was a source of pride for Chinese and began the custom of wearing masks against contagion, Lynteris argues.

But it was SARS in 2003 that made mask-wearing ubiquitous in recent times. I was in Hong Kong at the time, and no one went out without a mask. However, it has never been shown that the wearing of masks was significant in winning the battle against SARS.

The PRC government position is that before hospital personnel realized there was a coronavirus outbreak, many hospital workers contracted the disease and dozens died. The government then mobilized 20,000 doctors and nurses from the rest of the country to go to Wuhan to deal with the epidemic, and all used masks, eye shields and gowns, and none of them were infected. George Gao, a leading Chinese researcher, says it is a mistake that people in the West are not wearing masks, because asymptomatic and pre-symptomatic cases can spread the virus.

There are three issues with having everyone wear masks. First, the medical effectiveness of ordinary people using masks and N-95 respirators is not clear. This MedpageToday article from 2009 shows how contradictory the evidence has been, with many tests showing no benefit to wearing a surgical mask to avoid contagion.  A recent Lancet article includes a box that shows most countries agree there is no benefit to the public from wearing masks.

But then you have non-medical commentators, like this AI entrepreneur, who think the argument for wearing masks is clear, and who calls for everyone to wear masks. (It's funny how people successful in one field, especially rich people, show no hesitation about propounding on other areas outside their area of expertise.) The problem with masks is that if they are not worn, removed and disposed of correctly, they are of little use. The “best” masks, the N-95 respirator, makes it very difficult to breath if it is worn properly, with edges sealed. (And one cannot have facial hair and seal the edges.) Some have said (and I know from experience) that even walking is difficult when wearing the N-95, if it is worn properly.

The second issue is the shortage of masks in the US. When Covid-19 struck, the government stockpile of N-95 and surgical masks was way down because of a failure to restock after the 2009 Avian Flu epidemic (blame for this can be spread widely). The CDC and other authorities’ recommendation was that the general public NOT wear masks, and that they leave them for the health professionals who really needed them. There are horrifying reports of many hospitals and nursing homes where staff have to reuse masks. By comparison, during SARS, we were told in Hong Kong that we should replace the mask once it became wet from our breath, roughly every two hours. So one can’t help wonder whether the calls for the public not to wear masks are because of a kind of rationing, giving priority to those who benefit the most, rather than that the masks do not help at all. But of course the argument that they do not help long precedes the coronavirus crisis.

Third, there is the issue of the image of masks. Americans have been giggling about Asians wearing masks for years, and I’ve noticed that in a number of cases of reported anti-Asian incidents, the victim was wearing a mask (on 'maskphobia' see here). A number of Chinese friends have been shocked at Americans’ reluctance to wear masks. This humorous video sums up American’s views on the wearing of masks. 
The lyrics say:
Don’t wear masks
They don’t work
(and plus you look like a jerk)
You might think you’ll help a billion
but you scare the little children!
While in Asia, wearing a mask is seen as pro-social, protecting others from one’s own possible infection, in the US it is a sign of being sick. Americans have a strong antipathy towards medical masks, which is surprising because everyone wore a mask during the 1918 pandemic (see here and here). This crisis may well change American attitudes.

The anthropologist Gideon Lasco has noted
People’s motivation for wearing these masks goes far beyond simple considerations of medical efficacy. Cultural values, perceptions of control, social pressure, civic duty, family concerns, self-expression, beliefs about public institutions, and even politics are all wrapped up in the “symbolic efficacy” of face masks.
Which leads me to wonder if libertarian and other Americans skeptical of the government will not resist and even refuse to wear a mask. The same people who think Covid-19 is "political" will see wearing a mask as some sort of government plot. Already skeptical of science, they will wonder why the establishment has changed its mind on masks.

Interestingly, US hospitals have rules against medical personnel wearing masks that seem to focus primarily on not scaring other patients and avoiding the impression the hospital is germ-filled. Several doctors who insisted on wearing a mask in hospital hallways have been disciplined and fired, though it seems some hospitals have reversed themselves. As this NYTimes article today puts it: 
Amid the confusion, furious and terrified, doctors and nurses say they must trust their own judgment. Administrators counter that doctors and nurses, motivated by fear, are writing their own rules.
As the article notes, some hospitals are insisting that masks are not necessary, and are insisting on all staff sticking to the rules. Other hospitals are allowing, or even recommending, that caregivers wear surgical masks at all times at work.

This article from WebMD yesterday (30 March) says that wearing even a homemade mask might help, but hand washing and keeping distance from others are more important. Many reading that article will think, “Better safe than sorry,” and decide to wear a mask.

Since we will not eliminate the virus but can only try to control it, i.e. prevent its rapid spread, I can’t help but wonder, after the “stay at home” rules end on April 30, will the mask will become required when in public? We face many months of continuing, albeit hopefully low level infection, until a vaccine is developed or sufficient immunity in the population allows the epidemic to burn out. Already an article from 20 March in The Lancet argues for widespread use of masks, calling it a “rational recommendation”:
“As evidence suggests COVID-19 could be transmitted before symptom onset, community transmission might be reduced if everyone, including people who have been infected but are asymptomatic and contagious, wear face masks.”
Interestingly, of the six co-authors, two are based in Hong Kong (the rest in the UK) and five have Chinese names (the one Anglo name is based in Hong Kong). One wonders how much Asian attitudes towards masks influenced their recommendation. Conversely, one wonders what cultural attitudes make Western medical researchers resistant to the generalized wearing of masks. This really shows how cultural attitudes can influence scientists' judgement.

It seems we are close to a tipping point where everyone in the US will be allowed, or even encouraged, to wear a mask. But it will be hard to know if it is medically advantageous and appropriate, or is being done primarily to make people feel protected and more in control. But first the country needs a supply of masks.