SCOTT SIMON, HOST:
With the delta variant fueling a dangerous new surge in the United States, a growing number of health experts are urging more Americans to mask up all over again. But it's just not whether somebody wears a mask or not; it's whether they're wearing a good mask. We're joined now by NPR health correspondent Rob Stein. Rob, thanks so much for being with us.
ROB STEIN, BYLINE: Good morning, Scott.
SIMON: And let's please begin by reminding everybody what it is about the delta variant that is especially dangerous and why this should bring up the question of masks again.
STEIN: Yeah, the delta variant spreads incredibly easily - about twice as easily as the original virus. And the first thing I should say is the best thing anyone can do to protect themselves is get vaccinated. The vaccines look like they still work really well at preventing people from getting really sick or dying. But it looks like one reason delta's so contagious is that it grows really fast, so infected people could be walking around with a lot of virus in their bodies - like a thousand times more virus - which means they could be spewing out much more virus, making it way easier for someone to catch it from them.
Linsey Marr is at Virginia Tech University. She studies how viruses spread through the air.
LINSEY MARR: Delta transmits in the same way as the other variants that we've seen so far. It's just that people who are infected seem to release a lot more virus into the air. So masks still work, but with delta, we need better-performing masks.
STEIN: So Marr says everyone should take a good look at their mask to make sure it's good enough. A mask that filters out, say, 75% of viral particles might've been good enough before delta, but with delta, you really need a mask that's going to filter out something more like 90%.
SIMON: So what kind of mask would that be? Because a lot of people have gotten very used to using cloth masks or maybe surgical masks. Do they need to switch to something more like the N95?
STEIN: Well, those are the gold standard, and so are similar masks, like those KN95s. But Marr says cloth masks can still do the trick as long as they fit really well and they're made out of the right stuff.
MARR: Which means something that has a dedicated filter layer and that fits really well with no leaks.
STEIN: So it can't fit loosely, you know, leaving gaps on your cheeks or under your chin where the virus could sneak in, and it should pinch tight over your nose. And if you're wearing a cloth mask, it should have a layer made out of special filter material, not just regular cloth. If you're not sure, you can hold your mask up to the light to see if you can see pinpricks of light through it. If you can, then it's probably not good enough. Or, you know, another thing you can do is spray water through it in front of a mirror. If water gets through to the mirror, not good enough. Buy a better mask or buy filters to insert between the cloth layers. And if you really want to protect yourself, you could consider double masking.
SIMON: Rob, will the CDC change its guidelines that essentially say vaccinated people don't need to wear masks?
STEIN: Well, so far the CDC's sticking to that. But many experts want the CDC to go further and recommend vaccinated people wear masks, especially indoors, maybe tell localities to issue mask mandates where rates of vaccination are too low or rates of infections and hospitalizations are getting dangerously high.
SIMON: NPR health correspondent Rob Stein, thanks so much.
STEIN: You bet, Scott.
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