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CDC Takes Down Its Guidance On Aerosol Transmission On The Coronavirus


On Friday, the Centers for Disease Control and Prevention briefly became the first major health organization in the world to say the coronavirus might be spreading frequently through the air. Over the weekend, the CDC website said that COVID-19 spreads commonly through particles expelled when people talk or cough or breathe and that these particles may travel farther than six feet. Then today, the CDC dropped that guidance from its website. Well, here to talk about aerosols and confusion at the CDC is NPR's Pien Huang.

Hey there, Pien.

PIEN HUANG, BYLINE: Hi, Mary Louise.

KELLY: So more please on what the CDC posted and then deleted.

HUANG: Yeah, absolutely. So on Friday, CDC's website was changed to say that aerosol spread might be one of the most common ways coronavirus is spreading. And, remember, for a long time now, the public has been hearing that the coronavirus mostly spreads through droplets, like when somebody sneezes or coughs on you, or through touching contaminated surfaces. That has been the CDC's position. But the idea that the virus could in certain settings be spreading through the air is something that researchers have been considering for many months now. So superspreading events where a lot of people are getting infected at once seem to be happening in crowded, mostly indoor settings. And researchers say that that's probably because people across the room are breathing in clouds of the aerosolized virus particles wafting through. CDC's website now says that the aerosol guidance was posted in error, and they're still working on figuring out what to say about airborne transmission.

KELLY: Still figuring out what to say. And let me pause you there because what is there to figure out? I'm remembering back in July, the World Health Organization, for example, acknowledged that airborne spread in some capacity was possible.

HUANG: Absolutely. And they said that that was possible, you know, in some settings. And there still are questions about how long the virus lingers in the air, how far it travels through a room, how much you need to breathe in to get infected and also, very critically, how frequently it spreads this way, you know, through the air to people more than 6 feet away. And like you said, you know, CDC and the World Health Organization have for a while now been saying, like, hey, it is not a good idea to pack a room with people who aren't wearing masks. But they have stopped short of saying that the virus is commonly airborne. Linsey Marr, who's an aerosols researcher at Virginia Tech, she and some colleagues have been pushing for health agencies to recognize that the virus spreads through the air.

LINSEY MARR: Those in public health have thought that if they say a virus is airborne, it's going to cause panic, and a panic could be worse than the disease itself.

HUANG: She says that past researchers haven't spent a lot of time studying how aerosols spread disease, so it's kind of unknown and a little bit mysterious. And she also says that labeling the coronavirus as officially airborne might require hospitals to take more precautions than they're currently taking. But in not acknowledging airborne spread, she says that public health agencies aren't providing information that might really help stop the virus.

KELLY: So to make this practical, what does this mean for me, for you, when we're out in public?

HUANG: Yeah. Well, on a personal level, the recommendations people have been getting for months still apply. People should avoid crowded indoor situations. They should wear masks to cover their noses and mouths. The big difference Marr says is to make sure that there's good ventilation in all of our public buildings.

MARR: And this can be as simple as opening doors and windows. It can be adjusting dampers in HVAC systems so that you bring in more outdoor air.

HUANG: A lot of schools and restaurants and office buildings have been thinking about ways to improve airflow. But when the public health guidance doesn't specifically address airborne transmission, it leaves local health authorities on their own making judgment calls.

KELLY: Yeah. And just briefly worth noting, Pien, this is not the only guidance the CDC has walked back recently.

HUANG: No, it is not. Last Friday, they reversed some controversial testing guidance they posted in August around whether people without symptoms should ever be tested. The answer is yes. We've also seen reports of political operatives trying to insert themselves into CDC science papers trying to spin public health messages to make the president's pandemic response look better. And while CDC says this aerosols guidance was a draft that was posted by mistake, it's yet another very public and visible reversal, which doesn't help the agency establish the public trust that's really needed right now.

KELLY: Thank you, Pien.

HUANG: Thank you so much.

KELLY: That is NPR's Pien Huang. Transcript provided by NPR, Copyright NPR.

Pien Huang is a health reporter on the Science desk. She was NPR's first Reflect America Fellow, working with shows, desks and podcasts to bring more diverse voices to air and online.