The Aerosol Transmission Debate

We have known since the beginning of the pandemic that COVID-19 spreads from person-to-person. But doctors and scientists are learning more about whether this is happening only by droplet transmission or if the novel coronavirus can also spread by aerosol transmission. 

What’s the difference? Both droplet and aerosol transmission mean that the virus is spread through the air by saliva and mucus released as you speak, cough, or sneeze. Droplet transmission is defined by larger particles. The larger particles don’t travel very far in a room, and they fall from the air more quickly than smaller particles. Aerosol transmission is defined by smaller particles (less than 5 microns--that’s one millionth of a meter). The smaller particles can travel farther in a room, and they remain floating in the air for longer.

For some time now, health care workers have thought that aerosol transmission is possible in certain medical situations (like caring for patients on ventilators). A group of more than 200 scientists issued an open letter on July 7th saying that the research showing aerosol transmission in the community is now compelling. Scientists at the WHO say more data is needed to settle the question.

For most people, the answer to this scientific debate probably won’t make a huge difference in the way you’re working to keep your COVID-19 risk low in your everyday life. You still reduce your risk by maintaining social distance, spending time outdoors instead of indoors, reducing the number of people you spend time with, and wearing a mask. 

Regardless of the details on transmission, the conclusion remains the same: the novel coronavirus travels through air and you can become sick after inhaling it.


Last update: July 10, 2020, 12:53pm ET

Science review: GSN, JAB