Understanding the Risks

A Facebook friend posted this article from the blog “Elemental,” with the comment that it convinced him to give up his weekly tennis game because he “finally could not ignore” his glasses steaming up when he put a mask on. Now my friend is probably wise to have been taking extra precautions all along; he is in his late seventies and he may have underlying health problems. My problem with the article and the reaction is that I think it shows a real but common misunderstanding of what the scientists are saying about viral transmission. This is helped, of course, by the sensationalist title, “Six Feet Is Not Enough and 15 Minutes Is Too Long: The coronavirus ignores this outdated social distancing measure.” The blog is the work of journalist and crime writer Robert Roy Britt, whose self-reported mission is to “explain complex science and health stuff, concisely.” I think this is a good aim and not that different from my own self-description. The problem is that when you’re presented with the uncertainties and probabilities that are a feature of real life, you can always find an alarming way to pass that information on, and it doesn’t do much to educate the public.

Britt goes on to present his interpretation of the CDC’s updated definition, for contact tracing purposes, of “close contact”: “The new definition: 15 minutes or more of cumulative exposure to infectious individuals, within six feet, in a 24-hour period — such as three five-minute exposures — still regardless of masking and whether the contact was inside or outdoors.”

None of this is incorrect, and Britt supplies the links so that people like me can go back and look at the CDC’s website and the publication of the study that motivated it, which is all good. But he still accumulates the “facts” in such a way that it led my friend to decide his steaming glasses were a sign that his mask didn’t work to stop viral transmission. And this is where the extremely cautious meet the mask deniers. “Nothing works,” the deniers say, “so there’s no point in social distancing or mask wearing.” And that belief has been debunked time and time again.

So let’s look at what the truth is and what is really going on. First, the six feet or two meters: anyone who’s been paying attention knows that the likelihood of being infected with the virus diminishes with the distance you are from an infected person. Two meters has been identified as the distance needed to be reasonably sure you would not be exposed to enough viral matter to infect you. This article published by the National Institutes of Health is one of many that examines a variety of characteristics, including height differential, droplet size, viral load, and ventilation, and identifies a curve of probability of exposure. It seems that all else being equal, you are somewhere between 70 and 80 percent likely to be protected by maintaining a two-meter distance from an exposed person, but that can change depending on all the other conditions. Obviously, the risk is not zero until you are so far away that you couldn’t possibly interact with that person, and even then, if that person had been there an hour earlier, in just the right conditions, there is a miniscule risk of transmission. That’s why people were wiping down their groceries with disinfectant during the first lockdown.

One step that impedes but does not eliminate the spread of the virus is wearing a mask. This is common sense. In a non-COVID world, it’s pretty obvious that the reason we want people to sneeze into handkerchiefs is because they won’t spray us. The handkerchiefs aren’t made of medical-grade material, but they still stop most of what is expelled from getting to us. And there have been plenty of studies, like the one explained in this June paper in Nature, that support this point. As a matter of fact, my friend’s steamy glasses actually provide evidence that his mask is providing a forward-facing barrier to his breath. Yes, his glasses are steaming because it doesn’t fit perfectly around the bridge of his nose, and that means that some of his breath will escape, but even that is far more likely to land on him than his neighbor. He’s breathing out, and normally, his glasses wouldn’t steam up because all those droplets are disbursing in the air. But now, they’re trapped by the mask and end up back on his face. That seems to me to be a good thing. Again, it’s obviously not perfect, but it has an effect.

Ah, you say, but that protects other people from me—and I’ve been isolating, so it’s extremely unlikely that I’d have the virus anyway. But how can I protect myself from other, not-so-cautious people? Again, the answer may lie with masks. Back in a September post, I shared  research by Dr. Monica Gandhi of the University of California at San Francisco that suggests that wearing a mask might not prevent people from catching the virus, but it may lessen the severity of their illness by decreasing the “viral load,” or amount of virus they actually inhale. The idea of viral load (and a shortage of personal protective equipment early on) may explain why so many young, healthy healthcare professionals became seriously ill or died with COVID, while in the general population, there weren’t that many young people showing symptoms. The healthcare professionals were obviously coming into significant prolonged contact with people who were shedding great quantities of the virus.

Masks and social distancing do work, but they don’t eliminate the risk from the virus. The CDC study that Britt references was published in an appendix, and if you look at the comments Britt reports, they are all concerned with contact-tracing implications. The study itself is fairly easy to read (and fairly limited in its scope). It also contains a number of factors unlikely to occur in most people’s daily lives (except, perhaps, at a big, maskless political rally or celebration). Let’s look at some of the specifics: All of this took place in one correctional facility, mostly (obviously) indoors, and probably without great ventilation. The correctional officer identified as having contracted the virus had multiple contacts with infected prisoners (IDPs or “incarcerated or detained persons”). In the general population, we rarely come into contact with multiple infected people because the strangers we briefly encounter have all been fairly widely disbursed before we come into contact with them. In a correctional facility, the people the correctional officer encountered had probably encountered each other for multiple brief periods, making it more likely that a virus might spread. Also, although IDPs wore masks in many of the encounters, there were encounters at close range, as in doorways, where the correctional officer wore a mask but the IDP did not. Finally, although the correctional officer showed symptoms, he never became severely ill, so perhaps the fact that he wore a mask limited his viral load even though he had more than the threshold level of exposure at close range and with little ventilation.

Britt further muddies the waters by reporting that the CDC is not making a distinction between maskless and masked contacts or between indoor and outdoor contact. But if you look at the CDC’s explanation, you’ll note that there’s nothing new about this. They are contact tracing and identifying “close contact” for that purpose. Certainly making a distinction based on mask wearing would not be advisable, both because people misreport how well they follow guidelines and because we’ve all seen people with masks under their noses or, worse, below their chins so they can shout into a phone (expelling droplets in the process). When you’re contact tracing, it’s always better to err on the side of caution. The same is true of the “indoors versus outdoors” argument. You’re certainly better off outdoors, with good ventilation, but outdoors is also where joggers are and people crowd into lines, etc., and it’s better to over-identify than under-identify. But this is for the purpose of making policy regarding whom to test and when to trace contacts, not for giving advice to individuals.

What does the CDC advise to individuals? If you go onto their website and click the link for COVID-19 information, this is what you will see:

As it has consistently for quite a while now, the CDC advises people to wear a mask, avoid close contact, and wash your hands. They are updating how they need to deal with the virus overall, not how you as an individual should deal with the virus. On their website, you will also find specifics for people with underlying conditions, older people, etc. So my friend may read those guidelines and decide that for him, the likelihood of becoming seriously ill if he contracts the virus doesn’t make it worth the risk. What he shouldn’t do, though, is think that it means there was anything in that study that suggested the risk of an outdoor tennis game is higher because his glasses steam up when he wears a mask. And when he shares something like that on social media, it becomes a big game of “telephone” that allows misinformation to spread and panic people, at great cost to businesses, children whose education is impeded, and even people like my friend, who may risk more harm to his health by ceasing to exercise than he would by engaging in a socially distanced outdoor game of tennis.

This is where I think trustworthy leadership is important. People have been lied to so much over the course of this pandemic that they are either suspicious that the virus is dangerous at all or suspicious that they might be misled into making a life-threatening mistake because of political gamesmanship. I started to write this post before the very welcome news that the COVID-19 vaccine Pfizer has developed has had a 90% effectiveness rate in trials:

There are also a number of other vaccines pretty far along in the pipeline. All of the people who have worked to develop these vaccines have a strong base in math and science. Let’s hope that this pandemic—and the misconceptions and misinformation surrounding it—make it clear that we need to make sure more people have that strong base going forward.

2 thoughts on “Understanding the Risks

  1. There’s a lot to consume here – almost certainly too much and too detailed for the average person to readily consume – and when you get to the NIH report… I can’t prove it, but I wager that there have more studies conducted and articles written about C-19 than any other single topic in any single 10 month period. That’s why what people are told to do, and the way they are told needs to be simple, explicit and enforced. Wear a mask, stay away from people, avoid indoor spaces unless vital etc.

    Just to add another study – in this case the correlation between mask wearing and C-19 symptoms… https://l.facebook.com/l.php?u=https%3A%2F%2Fwww.washingtonpost.com%2Fbusiness%2F2020%2F10%2F23%2Fpandemic-data-chart-masks%2F%3Futm_campaign%3Dwp_post_most%26utm_medium%3Demail%26utm_source%3Dnewsletter%26wpisrc%3Dnl_most%26carta-url%3Dhttps%253A%252F%252Fs2.washingtonpost.com%252Fcar-ln-tr%252F2c4b72b%252F5f92fd6e9d2fda0efb521285%252F5d56b5c4ae7e8a3694b30c64%252F8%252F71%252Fed9fabc6ba77638b1d80ab4c91354c99&h=AT0DfL1eFRDIghqd4KTszpot69tgUd-_EjJuTmh4H2mVWnmxb1K5j5ZkgFiViojGLwHT_f18r9TZnqfNh8-mi24B6u163AquT_e_-9eAJGXW6BIJUuiLyni8SzctHx9Jpw&s=1

    Liked by 1 person

    1. Yes, this is a good study. I would say follow the official advice but also approach other information skeptically and always try to differentiate between people marketing their material with overly dramatic headlines and people trying to explain the underlying research. I would have to spend a long time to understand all the math, but we all should be able to understand the conclusions.


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