Does Wearing A Mask Keep You From Getting Sick? : Short Wave A new paper and growing observational evidence suggest that a mask could protect you from developing a serious case of COVID-19 — by cutting down on the amount of virus that takes root in your body.

Katherine Wu reported on that evidence for the New York Times.

Email the show at shortwave@npr.org.
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Wearing A Mask Could Be Even More Important Than We Thought

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Wearing A Mask Could Be Even More Important Than We Thought

Wearing A Mask Could Be Even More Important Than We Thought

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MADDIE SOFIA, HOST:

You're listening to SHORT WAVE...

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SOFIA: ...From NPR.

My mask protects you; your mask protects me. That's basically how we were told to think about face coverings when CDC first recommended wearing them.

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PRESIDENT DONALD TRUMP: The CDC is advising the use of nonmedical cloth face covering as an additional voluntary public health measure. So it's voluntary. You don't have to do it.

SOFIA: This was way back on April 3.

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JEROME ADAMS: This is all about me protecting you and you protecting me.

SOFIA: Surgeon General Jerome Adams put it this way.

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ADAMS: If people voluntarily choose to wear a face covering, they're wearing it to protect their neighbors from getting the coronavirus because, again, they could have asymptomatic spread.

SOFIA: Basically, we knew masks could help prevent big clouds of spitty virus particles from flying out of the mouth of an infected person. But our understanding of the virus was so new that we weren't as sure masks protected healthy people from getting the virus if they encountered those clouds of virus particles.

KATHERINE WU: Yeah. It's kind of interesting, the main messaging - and I think that it's still largely the case in a lot of places - is that masks are better for the other. It's almost like a public service, I've heard people say over and over.

SOFIA: Katherine Wu is a reporter for The New York Times. She recently wrote about a new scientific paper and a bunch of observational data from around the world that supports the idea that masks are even more important than we initially thought - that they don't just protect other people; they protect you, too.

WU: Right. So the researchers I talked to have this really interesting theory, and the theory is kind of this idea that, you know, the dose makes the poison. So the fewer viral particles that hit you, the less virus is going to kind of set up shop in your body. And that sort of smaller dose makes it less likely that you're going to have severe symptoms.

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SOFIA: This episode - how a mask could prevent severe symptoms of COVID and what this development reveals about the way science works.

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SOFIA: I'm Maddie Sofia, and you're listening to SHORT WAVE, the daily science podcast from NPR.

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SOFIA: The case that a mask can protect the person wearing it is laid out by scientists in a new paper coming out soon in the Journal of General Internal Medicine. Katherine Wu wrote about that paper, which ties together three different concepts about viruses and how they work. The first is the idea of viral dose.

WU: That's kind of the amount of virus that is hitting your face parts (laughter)...

SOFIA: Right.

WU: ...And the amount of virus that you're exposed to.

SOFIA: The second concept is viral load, basically the amount of virus that has set up shop in your body after you get infected.

WU: Exactly.

SOFIA: The third idea, which is not new to scientists who study viruses, by the way, is that cutting back on the viral dose might mean that even if you get the coronavirus, your immune system will react in such a way that you won't get as sick.

WU: This idea that you can encounter a tiny, little bit of virus and your immune system's going to have just a way easier time wrangling those kind of few invaders at a time.

SOFIA: Right.

WU: And so it's less likely that your body's going to struggle to control the infection and less likely that you are going to get really, really sick.

SOFIA: Again, not a new concept for scientists. But what is new is the coronavirus itself. Remember how we all called it novel for those first few months? Scientists had never seen this coronavirus before, so saying masks might protect the wearer doesn't mean that scientists are just changing their minds. As Katherine and I talked about, it means that each day, they're learning more and more about the virus. But things like viral dose and viral load are really hard to study.

WU: Yeah, absolutely. And this research is fascinating. I think the trick here is we have so much data that seems like it could support this idea, but a lot of it is totally observational.

SOFIA: Right.

WU: People are looking at how much virus do you have when your symptoms start. When is the easiest time to test someone? But, you know, the kind of gold-standard experiment that people have done in the past with humans with, you know, maybe kind of shady ethics and are now trying to do with a bunch of animal models is you actually have to give a living creature different doses of virus...

SOFIA: Right.

WU: ...And see what actually happens to that animal or human, which is really hard to do.

SOFIA: Yeah. And, like, you know, we've - we know a little bit about the flu because there are actual studies in which they gave people certain amounts of these doses. But for coronavirus, because we don't understand the complications, we are - you know, and it's because it's such a deadly disease, we really can't do that, and people are really not comfortable doing that. So we do have some studies in animals. And one of the pieces that you talked about in your piece was this study out of China where researchers studied this idea using hamsters.

WU: Yeah, I thought this was actually a really cool study. These researchers basically put hamsters in adjacent cages. Some of them had the coronavirus, so they were infected in one cage, and then they were separated from their neighbors. And some of the cages had these little partitions between them made out of surgical masks. So the researchers did not put masks on the hamsters. Hamsters don't usually take kindly to that sort of thing.

SOFIA: Right.

WU: But it seems like they did kind of the next best thing. And it turned out that the hamsters that were separated from their neighbors by these surgical mask partitions were a lot less likely to get infected with the coronavirus in the first place. And the hamsters that still ended up getting infected with the virus - they had less signs of illness than their neighbors that weren't separated by these masks.

SOFIA: And there's, like, a little bit of nuance here, Katherine - right? - which is that if the masks had just prevented some animals from getting sick at all, you would say, like, OK, this makes sense to us. Maybe there weren't enough particles to get the little hamster sick. But, in fact, they did get sick. They just got less sick, which is kind of a piece of evidence for this idea of the dose makes the poison.

WU: Right. I think that makes a lot of sense. I mean, it's - it is a little bit tough because I don't think it's as clear-cut as to say, like, oh, if I get 10 viral particles on my face, I'm not going to get sick, but if I get 15, I'm going to get a little bit sick.

SOFIA: Right.

WU: And then if I get 20, I'm going to get super sick.

SOFIA: Right.

WU: No one knows those numbers yet. And those are absurdly low numbers, so feel free to stop me.

SOFIA: Yeah, those are measles numbers, Katherine, but keep going.

WU: (Laughter) Yeah, but, like, those are not clear-cut. And honestly, what numbers hold true for me are probably not going to hold true for you. It's super complicated.

SOFIA: Right.

WU: I think what researchers are trying to get at here are super broad trends at a population level.

SOFIA: Yeah, yeah. Because whether or not one, like, person has more severe symptoms to the other could be based on a lot of different things because the immune system is endlessly complicated, as we talked about the last time you were on the show.

WU: Right, absolutely.

SOFIA: And so there's also these observational studies, right? So these are not scientific experiments that are being done, but these are people trying to kind of look at these huge datasets we have and see, OK, here are a couple of different variables. What could they be? And so there are some that are around this idea of infectious dose. I mean, you described a situation in a seafood plant in Oregon. What happened there, Katherine?

WU: Yeah. So during, you know, these really, really big-scale outbreaks that were happening at, like, meat processing plants and other food processing plants, a lot of employers wised up pretty quickly to this idea that these, like, very crowded insular environments are pretty high-risk for spread. And so they started giving out masks to all their employees so that they could work with, you know, some degree of protection.

There did end up being an outbreak at this seafood plant in Oregon, but more than 90% of the people who tested positive for the virus didn't end up having symptoms, which is pretty extraordinary considering that, you know, the CDC is still trying to really nail down this number. But they've put out some recent tentative estimates that maybe about 40% of the infections that we know about are asymptomatic. That's a huge difference between 40% and 90-plus percent.

SOFIA: Yeah. Definitely, definitely. And the other thing, you know, the other piece of data that, again, is very correlative and we're not - we're still working to understand this is that you pointed out that more mask-wearing in the U.S. has coincided with relatively fewer deaths than at the beginning of the pandemic, although that's, you know, a very complicated thing to prove, right?

WU: Yeah, that is - I think that's something people have been talking about a little bit over the past few months. There's a lot of factors that could go into this. You know, we're much better at treating this virus, and there's some evidence to show that the average age of the infected person has gone down, and we know older people are more susceptible to really severe COVID-19.

SOFIA: Right.

WU: But so many more people are also wearing masks now, and it's certainly possible that people are getting smaller doses of this virus on average, and maybe that's contributing to fewer symptoms and less severe disease and, thus, fewer deaths.

SOFIA: And we should probably say, Katherine, that the type of covering you're wearing matters, right? The type of mask that you're wearing does matter in how much protection you have, right?

WU: Absolutely. That's a really good point. A lot of researchers have said, you know, you want to choose something thick that's got a couple layers to it. You want to have it fairly tight over your mouth and your nose. It's OK if it's a little loose-fitting. We don't want to make it really uncomfortable for you. But you want it to sort of seal off your mouth and your nose, which means covering all of those holes in front of your face.

SOFIA: Right.

WU: And when you actually put it on and take it off, try not to touch the front of it because that's where all the stuff that you're trying to keep out of your nose and mouth has probably accumulated. Instead, grab those ear straps or whatever is keeping it on your face.

SOFIA: Yeah, absolutely. And, you know, Katherine, I do think there's a bigger thread here, and I want to ask you because you're a scientist-turned-journalist, just like me, and it's, you know, about how science is done and interpreted in a pandemic. You know, science is so much of not knowing what's going on and learning little pieces at a time, and going back-and-forth on an issue before you arrive at a conclusion is actually very, very common. I mean, it is my - I mean, I don't know, Katherine. That's how it was in graduate school for me.

And so this idea that, like, because, you know, people don't know what they're talking about with masks or, you know, like, the CDC is changing up their guidance, like, it's - I - you know, it's frustrating, but it's also how it works. You know what I mean?

WU: Yeah, absolutely. I think the most tumbling thing I had to go through in the process of becoming a scientist was just getting more comfortable with being wrong all the time and then talking about being wrong all the time because I think if I didn't feel empowered enough to talk about my mistakes with other scientists who could, you know, broaden my perspectives, I wouldn't have ended up learning anything.

SOFIA: Yeah.

WU: But, you know, to kind of flip that on its head, I think it's just been incredibly humbling and incredible to watch how the scientific community has come together. Science is often so plodding and tough. And, you know, sometimes a paper will be published, and then eight years later, data will come out that'll show the story's a little bit different here.

A lot of that timeline has been collapsed into just a couple months for this pandemic, and people are coming together from around the world to learn as fast as possible. Part of that learning process is going to involve, you know, mistakes and revisions and tweaks. But it's kind of amazing to see everyone coalesce into this giant brain around the virus right now.

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SOFIA: All right, Katherine Wu, you know I appreciate you, I appreciate your brain. Thank you for your reporting, and thanks for your work.

WU: Thank you so much for having me. It was a delight to be here again.

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SOFIA: There's a link to Katherine Wu's story about masks and viral dose in our episode notes.

This episode was produced by Brent Baughman, fact-checked by Abby Wendle and edited by Deborah George. I'm Maddie Sofia. Back tomorrow with more SHORT WAVE from NPR.

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