A Scientist Explains Why You Should Cover Your Face

Why exactly should we wear masks? Is it mainly to prevent us from infecting others? Or is it mainly to prevent us from getting infected?

We asked University of San Francisco data scientist Jeremy Howard (whose Twitter handle currently reads Jeremy #MasksForAll Howard) about what masks — homemade or otherwise — do to protect ourselves and others from disease.

Here's what he told me:

"It's mainly to help others — you're doing the right thing by your community.

Think about it this way: We know that the spread is from the little micro droplets of saliva when you're talking. If you have something over your face, obviously they're gonna hit the mask and not the person you're talking to. If it touches their eyes or their nose or their mouth, they're likely to get sick.

And we see that for things like this Seattle choir rehearsal, where 45 out of the 50 people got sick. Because, of course, when you're singing those droplets are flying around. On the other hand, does it protect you? Yes, it does quite a bit. But it is possible that this very breathing-in process could cause particles to kind of sneak in behind the mask. So you should definitely wear them to protect yourself, but mainly to protect your community.

Because if you're not doing that, you're placing the people around you at risk by failing to wear a mask."

I don't think that when I'm speaking normally, like I'm speaking to you right now, that I spit or let out droplets.

"Yeah, we would all like to think that because it sounds kind of gross. But, I'm afraid to say, you and I talking right now are being kind of gross. When you actually study under a laser system what's coming out of our mouths, there's little droplets. In fact, sometimes you'll see on your laptop computer screen little dried-up circles when you clean it. That's the droplets that are coming out of your mouth.

Everybody does it in every language. It's been tested in scientific situations — low volumes, high volumes, Russian, Czech, English, Chinese. We are all spitting out little droplets of saliva all the time. And they're landing on our friends' and families' faces."

Howard also pointed out something notable he's seen while studying the data on COVID-19 from around the world. Even though Japan doesn't have good testing in place and is not practicing social distancing, the nation of 127 million people has just 77 deaths as of Sunday.

Why? Howard says it's because Japan is wearing masks. Compared to the steep death toll in New York, he calls it "a stark, stark difference."

This interview aired on our newsroom's local news show Take Two, which A Martínez hosts. Listen to KPCC by tuning your dial to 89.3 in the L.A.-area, asking your smart speaker to "play KPCC" or streaming here.

MORE ON HOMEMADE MASKS

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• Check out Take Two's gallery of homemade masks