CDC acknowledges that COVID-19 can spread through the air

Two weeks after removing language that acknowledged COVID-19 spreading through aerosols, the Centers for Disease Control and Prevention officially added a new section to its website Monday declaring that “COVID-19 can sometimes be spread by airborne transmission.”

The update reads: “Some infections can be spread by exposure to virus in small droplets and particles that can linger in the air for minutes to hours. These viruses may be able to infect people who are further than 6 feet away from the person who is infected or after that person has left the space.”

The CDC updated its guidance Monday to include aerosols as a route of transmission for COVID-19. Here's what you need to know. (Getty Images)
The CDC updated its guidance on Monday to include aerosols as a route of transmission for COVID-19. Here's what you need to know. (Getty Images)

The organization reaffirmed that the main route of transmission remains respiratory droplets, which are released through things like coughing and sneezing. These droplets, which are often larger in size, spread the virus through contact with a mucous membrane, such as the eyes or nose. Aerosols, which are smaller, can linger in the air for hours and can spread through inhalation alone.

Although more research is needed to determine exactly how prevalent airborne transmission is, the CDC now acknowledges that it can occur. “There is evidence that under certain conditions, people with COVID-19 seem to have infected others who were more than 6 feet away,” the CDC writes. “These transmissions occurred within enclosed spaces that had inadequate ventilation. Sometimes the infected person was breathing heavily, for example, while singing or exercising.”

Multiple outbreaks have been reported from choir practices, including one in Washington in early March that led to 53 COVID-19 infections and two deaths. The CDC elaborates on what may be happening at these events. “Under these circumstances, scientists believe that the amount of infectious smaller droplet and particles produced by the people with COVID-19 became concentrated enough to spread the virus to other people,” the CDC writes. “The people who were infected were in the same space during the same time or shortly after the person with COVID-19 had left.”

On Twitter, both epidemiologists and aerobiologists, who have at times disagreed on the issue, praised the CDC’s guidance. Dr. Kimberly Prather, director for the NSF Center for Aerosol Impacts on Chemistry of the Environment (CAICE) at the University of California, San Diego, tweeted that she was “feeling hopeful” in the wake of the CDC update, along with a newly published paper in Science urging the medical world to “harmonize discussions about modes of virus transmission”

Related: Fauci: 'Good enough data' on aerosol spread

Dr. Saskia Popescu, an infection prevention specialist at George Mason University, tweeted that the document is “important” and that it “sheds light on situational airborne (aerosol) spread, close contact as a driving factor, & prevention strategies.” She added that the new information “doesn’t change the recommendations” but “rather reinforces what we’ve been saying — mask, distance, avoid crowded indoor spaces, adequate ventilation, hand hygiene, and cleaning/disinfection.”

Dr. Amesh Adalja, an infectious disease expert and senior scholar at Johns Hopkins University Center for Health Security, agrees. “This is exactly what most of us have said from the beginning — that the primary way this virus spreads is through droplet transmission, and when there is airborne transmission, it’s in specific circumstances.” He says these circumstances can include “enclosed spaces with poor ventilation, where people are doing activities like singing or exercising.”

But even these instances, at least for now, seem to be unusual. “There are certain situations where airborne transmission occurs, but still the primary way that people are getting infected is close contact with individuals within six feet,” says Adalja. “What’s important to emphasize is that we don’t change the way we’re thinking about how this transmits; we’re just adding to it.”

The CDC’s update ends with information on how to stay safe, including remaining six feet away from others, covering your mouth and nose with a mask (which it says can help prevent close contact and airborne transmission), washing your hands often, isolating when sick and avoiding “crowded indoor spaces” as well as ensuring indoor spaces that you are in are properly ventilated.

“In general, being outdoors and in spaces with good ventilation reduces the risk of exposure to infectious respiratory droplets,” the CDC writes.

For the latest coronavirus news and updates, follow along at According to experts, people over 60 and those who are immunocompromised continue to be the most at risk. If you have questions, please reference the CDC’s and WHO’s resource guides.

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