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How Helpful Are Face Masks In Preventing The Spread Of Disease?

ARI SHAPIRO, HOST:

As the Wuhan coronavirus spreads, cities in China and other parts of Asia are reportedly running out of face masks. NPR's Maria Godoy looked into whether a mask can protect you from the virus.

MARIA GODOY, BYLINE: First, let's distinguish what kinds of face masks we're talking about. The Centers for Disease Control and Prevention recommends that health care workers interacting with a coronavirus patient wear a heavy-duty mask called an N95 respirator. They're designed to block small particles from entering the nose and mouth.

Dr. William Schaffner of Vanderbilt University Medical Center says wearing an N95 is serious business.

WILLIAM SCHAFFNER: We have to be fit-tested. We have to demonstrate that we know how to put them on and wear them. And they're difficult to wear. That's the kind of protection that really works.

GODOY: But what most people on the streets are wearing is something else - cheap, disposable surgical masks. And Schaffner says the evidence that these masks protect against infection is meager.

SCHAFFNER: The general sense is perhaps, but they're certainly not an absolute protection.

RAINA MACINTYRE: A mask will protect you against a visible splash or spray of fluid or large droplets. It's just a physical barrier.

GODOY: Raina MacIntyre is an infectious disease researcher at the University of New South Wales in Australia. She's studied the efficacy of face masks. She says surgical masks don't provide a tight fit. Small airborne particles can still get through. But her research suggests surgical masks can lower the risk of getting infected if you're at home in close contact with a family member who has a respiratory illness, but only if you wear the mask right.

MACINTYRE: Which means wearing it all the time when you're in the same room as the infected person.

GODOY: And being careful not to touch the front of the mask when removing it. Otherwise, you could end up contaminating yourself.

As for wearing a surgical mask outdoors in public, Marybeth Sexton of the Emory University School of Medicine says that's not necessary if you're in the U.S. or another country where the risk of catching the Wuhan coronavirus is considered low.

MARYBETH SEXTON: When you're out in the open air, you've got a lot of good airflow. It's really going to be in enclosed spaces with people who are contagious that you have the most risk of transmission.

GODOY: She says wearing a face mask is a good idea if you're ill and need to go see the doctor, but that's really to keep you from getting other people sick. Otherwise, she says, leave the face masks for the people who need them, like health care workers and people with symptoms, so we don't end up with mask shortages.

Raina MacIntyre says the calculation of whether to wear a face mask is different for people in a place like Wuhan, China, the epicenter of the current outbreak.

MACINTYRE: If it's someone in Wuhan, where most of the cases have been, then there might be some value to it. There's a lot of unknowns about this infection. That's the problem.

GODOY: And wherever you are, there is something that all the infectious disease experts I spoke with recommend we all do to keep from getting sick - wash your hands a lot.

SCHAFFNER: Hand-washing for sure - constantly, frequently, all the time; summer, winter, whatever.

GODOY: Maria Godoy, NPR News. Transcript provided by NPR, Copyright NPR.