Leaked Papers Indicate Coronavirus Transmission May Be Airborne: The Centers for Disease Control and Prevention recently updated its guidance on the novel coronavirus, adding airborne transmission to the list of ways it’s possible to become infected with COVID-19.
Similar guidance was posted last month but was quickly deleted after officials with the agency said information from a draft version was posted accidentally.
Doctors have long warned that COVID-19 can be spread through close contact — and the public has been strongly encouraged to wear masks — but it has taken longer for them to conclude the coronavirus can be passed through airborne transmission.
Here’s what you need to know about the different ways people can transmit the disease.
What is airborne transmission?
The most common way COVID-19 spreads is through close contact with infected people, mainly by droplets when they cough, sneeze, talk and exhale.
These droplets are relatively large — even visible to the naked eye. They fall to the ground quickly, usually within about six feet of the source.
But the CDC now says smaller droplets carrying the virus may be created that can linger in the air for minutes or hours, and can travel much farther on air currents.
Tuberculosis, measles, and chickenpox are diseases that spread efficiently in this way — which is sometimes called aerosol transmission — and health experts have been warning of increasing evidence that COVID may do the same.
In March, health experts pointed to an incident in Mount Vernon, Wash., when dozens of people got sick with the virus after about 60 healthy choir members gathered to practice.
A study published in The New England Journal of Medicine in April found that the virus can live in air particles up to three hours.
And in July, a group of more than 200 health experts wrote a letter urging organizations, including the World Health Organization, to acknowledge the possibility of airborne transmission.
The World Health Organization recognized airborne transmission in a brief published a few days after the letter.
How can you protect yourself?
The CDC notes that though getting infected by someone who is more than six feet away is possible, documented cases of airborne COVID-19 transmission were found in “limited, uncommon circumstances.”
Airborne transmission is more likely to occur in enclosed areas with poor ventilation where people have prolonged exposure to respiratory particles, the CDC said.
Activities that increase the number of particles in the air — singing, shouting or exercising, for example — can increase the risk.
“These transmission events appear uncommon and have typically involved the presence of an infectious person producing respiratory droplets for an extended time (greater than 30 minutes to multiple hours) in an enclosed space,” the CDC said.
“Enough virus was present in the space to cause infections in people who were more than 6 feet away or who passed through that space soon after the infectious person had left.”
Health experts say now-common public health recommendations, including wearing masks, frequent handwashing, social distancing and avoiding crowded, indoor spaces, are the best ways to protect against airborne transmission of of the coronavirus.
“This concept of ventilation is just so important,” said Kimberly Prather, director of the Center for Aerosol Impacts on Chemistry of the Environment based at Scripps Institution of Oceanography at the University of California San Diego.
“In some places that’s just a matter of opening the door and opening the window. Just having clear air is really the best thing you can do.”
She joined other health experts and researchers in calling for increased public guidance on airborne transmission.
“What if all of the people in that situation are smoking?” Prather continued. “Are you going to be exposed?
Will you breathe a lot of cigarette smoke? If yes, you need to do something to change the situation.”
The chief guidance on the coronavirus — that infection is more likely the longer and closer people are with each other — holds true, health experts say.
The most important thing to understand is that the six-foot social distancing recommendation isn’t a guarantee of safety and that the risk of getting sick depends on where someone is.
“There are a lot of factors that go into transmission, and you can’t cherry-pick which ones,” Saskia Popescu, an epidemiologist and biodefense expert at the University of Arizona, told CNBC.
“This is saying, ‘Hey, some environments are higher risk, so you need to take all of these safety measures,’ that risk reduction is additive, and not just to get so focused on one.”