Exactly How Airborne Is Coronavirus, Anyway?

From the early days of the coronavirus pandemic, we were urged to be wary of surfaces. Experts knew that SARS-CoV-2, the virus that causes COVID-19, could linger on door handles, shopping carts, and subway poles for hours, maybe days. But now, researchers are taking a closer look at how the virus travels through the air — and how likely it is to be transmitted through breathing.

On March 28th, the World Health Organization tweeted that "COVID-19 is NOT airborne," noting that it's mainly transmitted through droplets released when a person coughs, sneezes, or talks. They noted these droplets are too heavy to hang in the air; instead, they quickly drop onto surfaces.

But new research indicates that respiratory droplets can linger in the air for anywhere from a fraction of a second to minutes, according to a Journal of The American Medical Association article published on March 26. (They can travel too — up to 26 feet. That seemingly puts a wrench in that whole “six feet” rule we’ve all been following for social distancing.)

This type of droplet is just one piece of the puzzle, though. For coronavirus to be dubbed "airborne" by health officials, researchers would need to prove that the virus can be transmitted by micro-sized "aerosols." These are created when a droplet evaporates more quickly than it falls to the ground, leaving the virus suspended in the air.

These aerosols may remain airborne for up to four hours, according to preliminary research from The New England Journal of Medicine that has not yet been peer-reviewed. That's a far cry from the "minutes" the JAMA research suggested. It sounds scary, but researchers still don't know whether these aerosols are concentrated enough to actually infect people with COVID-19.

What's more, the WHO pointed out in a March 27 scientific brief that the aerosols in the NEJM study were generated by a machine "that does not reflect normal human cough conditions."

Ultimately, experts and officials need more facts and conclusive research to know whether coronavirus is truly airborne, explains Robert Korn, MD, vice president of emergency medicine at Northwell Health.

"The question [of whether coronavirus is airborne] has lots of caveats," Korn says. "From what we know from experimental research, if you're outside, it's probably not airborne because there's wind and it moves the little droplets away; they fall in a “shower’ up to 6 feet away from you, but usually not farther than that. But if you're in a room and the air is really still and there's eight people and two of them sneezed, the droplets may hang around a little longer and you could certainly walk through a wall of COVID," he continues. "There isn't a single answer to the question of whether it's airborne, because it depends on all of these factors, including the environment."

The Public Health Agency of Canada has not made it mandatory to wear a face mask in public however it is recommended to wear one as an added protective measure. In the U.S., the CDC recently changed their guidelines about face masks. Though previously they'd only suggested that select groups wear the protective coverings, now they were recommending that everyone don them when out in public, especially areas “where other social distancing measures are difficult to maintain” such as grocery stories, your local drugstore, and the park. WHO is also recommending that medical professionals take "airborne precautions" when doing certain procedures.

Steven Quay, MD, PhD, a physician, scientist, and biotechnology entrepreneur, emphasizes that current evidence shows that people are much more likely to pick up the virus from a surface than from the air. So continue to disinfect surfaces, wash your hands regularly, and avoid touching your face. But these new studies may give you extra incentive to steer clear of crowded indoor space and to abide by the new advice regarding face masks, too.