MARY LOUISE KELLY, HOST:
A lot of people are asking the question we are about to tackle in this next story - is all this mask-wearing really helping to curb the spread of coronavirus? NPR's Maria Godoy set out to answer that question.
MARIA GODOY, BYLINE: So states are opening up. And more and more, we're seeing people out and about without masks on. But folks, there is still a pandemic out there. And every expert I've spoken with says masks can help.
JEFFREY SHAMAN: It's very powerful as a tool to control the virus.
GODOY: Jeffrey Shaman is a researcher and epidemiologist at Columbia University.
SHAMAN: I personally think that face masks are a key component of the non-pharmaceutical arsenal we have to combat COVID-19.
GODOY: Now, it's understandable if some people remain skeptical since, at the beginning of the pandemic, public health officials in the U.S. said the general public didn't need masks. But that changed as it became clear that infected people can spread the coronavirus before they even show symptoms of COVID-19 or even if they never show symptoms.
Linsey Marr of Virginia Tech studies the airborne transmission of viruses. She says people can spread the virus even if they're just talking.
LINSEY MARR: If you're talking - when things are coming out of your mouth, they're coming out fast, and they're going to slam into the cloth mask. I think even a low-quality mask can block a lot of those droplets.
GODOY: Marr points to one study that looked at people infected with the flu and seasonal coronaviruses. It found that even loose-fitting surgical masks blocked almost all the contagious droplets they breathed out. A study published just last week found that if the majority of people wore face masks in public, that could dramatically reduce transmission of the virus.
Now, researchers will tell you that masks don't provide foolproof protection. And teasing out the science of masks will take time. But Linsey Marr says there's enough evidence already to say that, combined with measures like social distancing, masks really do help.
MARR: You know, I would be comfortable sending my kids back to school if everyone's wearing masks and they're staying as far apart as possible.
GODOY: The World Health Organization agrees. Earlier this month, the WHO changed its advice on masks. It now recommends that healthy people wear cloth masks in public, especially when they can't maintain social distance. Epidemiologist May Chu helped craft the WHO's new mask guidance.
MAY CHU: What we found was that you need to have several layers, and each of these layers can give you protection.
GODOY: Chu says a good option is a multilayer mask with a pocket. The inner and outer layers should be made of a tight-woven fabric. Cotton works well. In the pocket, use a filter, preferably a double layer of a material called polypropylene.
CHU: If you go to Walmart, look for Oly-Fun, which is the brand name of that fabric.
GODOY: That's spelled O-L-Y-F-U-N if you're taking notes. Chu says the fabric is great as a filter, but it has another benefit. It holds an electrostatic charge that can trap infectious droplets coming into or out of a mask. Another good option - take two sheets of tissue paper, fold them over and put them inside your mask.
CHU: The four layers of paper gives you adequate protection.
GODOY: Shape also matters. Masks that are cupped to fit tight to your face and those with pleats or folds both do a better job of filtering air than masks with flat fronts. And avoid masks with a valve in the front. That valve lets unfiltered air out, so it won't protect other people if you're contagious. And after all, protecting others is one of the main reasons to wear a mask in the first place.
Maria Godoy, NPR News. Transcript provided by NPR, Copyright NPR.
