CDC Says Coronavirus Airborne—Here's How the Guidelines on Transmission Have Changed | Updated

Update: Since this article was published, the U.S. Centers for Disease Control and Prevention has said it erroneously stated on its website that the coronavirus can spread through airborne particles. You can read about the reversal here. The article below has not been updated or amended.

The U.S. Centers for Disease Control and Prevention (CDC) has updated its guidelines for preventing the spread of the coronavirus that causes COVID-19, after it acknowledged that airborne spread of the coronavirus may be possible.

The CDC added the new information to its How It Spreads page on Friday.

What the CDC now recommends

The agency advises people to practice social distancing by staying at least 6 feet away from others whenever possible. Washing hands often with soap and water, or using a hand sanitizer that contains at least 60 percent alcohol when those aren't available, is also important, as well as staying home and isolating from others when sick. Routinely cleaning and disinfecting frequently touched surfaces is also advised, as is using air purifiers to help reduce airborne germs in indoor spaces. A mask should be used to cover the mouth and nose when around others, although this should not replace other prevention measures, it states.

The CDC also clarified the importance of asymptomatic spread, going from stating "some people without symptoms may be able to spread the virus" to "people who are infected but do not show symptoms can spread the virus to others."

Previously, the CDC said to keep a "good social distance" of around 6 feet, and cover the mouth and nose with a mask when around others while not stressing this should not replace other measures as it does now. The steps for hand-washing and disinfection have remained the same.

What the CDC says about airborne transmission

The CDC updated its website on Friday amid a debate among scientists on whether the coronavirus is airborne. It states the virus can be passed on "through respiratory droplets or small particles, such as those in aerosols produced when an infected person coughs, sneezes, sings, talks, or breathes."

Before, the CDC said the germ could pass "through respiratory droplets produced when an infected person coughs, sneezes, or talks."

The CDC now says: "These particles can be inhaled into the nose, mouth, airways, and lungs and cause infection. This is thought to be the main way the virus spreads."

It goes on: "There is growing evidence that droplets and airborne particles can remain suspended in the air and be breathed in by others, and travel distances beyond 6 feet (for example, during choir practice, in restaurants, or in fitness classes). In general, indoor environments without good ventilation increase this risk."

The CDC acknowledges "we are still learning about how the virus spreads and the severity of illness it causes."

Although the coronavirus can spread when droplets land on a surface and a person touches it and then their mouth, nose or eyes, this is not thought to be the main way it spreads, according to the CDC.

The debate around airborne spread

In July, more than 200 scientists called on public health bodies including the World Health Organization to recognize that the coronavirus that causes COVID-19 is airborne. The scientists wanted organizations to acknowledge that evidence suggested the coronavirus not only spreads in large droplets from coughs and sneezes that quickly fall under gravity, but there is "significant potential" that microscopic droplets could pass viruses on at short to medium distances, "up to several meters, or room scale."

In this context, airborne doesn't mean the same as it does for other diseases such as measles and tuberculosis, where viruses can spread easily over long distances.

Donald Milton, a professor of environmental health at the University of Maryland who was among the signatories of the letter, told CNN on Sunday that the CDC's change in language was a "major improvement."

He said: "I'm very encouraged to see that the CDC is paying attention and moving with the science. The evidence is accumulating."

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A stock image shows people social distancing and wearing masks. The CDC states these are two ways to prevent the spread of the coronavirus.