As scientists work overtime to learn about the novel coronavirus SARS-CoV-2 and how to fight it, our latest understanding of the virus constantly changes. Our understanding of mask-wearing is no exception. Let's dispel some myths.
MYTH: We don't actually know if masks can prevent the spread of COVID-19.
The more we learn about the virus and how it's spread, the more evidence we find to support the benefits of wearing a mask.
When we talk, we produce oral fluid droplets—a fancy word for spit—that can carry viral particles capable of infecting others. These droplets come in a range of sizes and the smaller droplets can travel further because they're lighter. One group measured just how far by highlighting the paths of spittle with lasers and high-speed video. (Check out their video if you want to be simultaneously amazed and grossed out.) They saw that speaking just one phrase—“stay healthy”—generated droplets as small as 20 microns and as large as 500 microns in size. But when the speaker placed a damp washcloth over their mouth, none of those droplets made it through.
Countries where mask-wearing is more of a cultural norm show lower death rates.
There's also some evidence to suggest that the same amount of droplets are produced when talking as when sneezing or coughing, activities we more commonly associate with viral spread. The evidence also shows that those speaking-generated droplets are smaller, which makes them capable of further spread.
But some epidemiologists argue that the strongest evidence for the importance of masks is looking at overall case counts in places where people wear masks versus places where people don’t. Countries where mask-wearing is more of a cultural norm show lower death rates. The increase in coronavirus cases in Washington, D.C. slowed noticeably after a mask mandate was put in place.
There are also studies of individual events where masks clearly prevented transmission. For example, two hairstylists in Missouri saw 140 clients while they were infected with COVID-19 and thus likely contagious, but not a single client tested positive. Everyone had been wearing a mask.
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