What 'airborne coronavirus' means, and how to protect yourself The COVID-19 pandemic has revived a decades-old debate about how respiratory diseases travel—which affects the safety practices experts recommend.
BY MAYA WEI-HAAS
PUBLISHED AUGUST 11, 2020
READ THIS SENTENCE aloud: With every passing word, an expanding blast of spittle spews from your mouth—the more emphatic the speech, the greater the spray.
This mouth-made mist is the subject of a great debate about how the coronavirus hitches a ride from person to person. Virus-riddled globs can be inhaled, or even land in the eyes, potentially sparking infections in others. But for respiratory diseases like coronavirus, it’s long been thought these droplets are so large they will fall rapidly to the ground, inspiring public health recommendations such as cleaning surfaces and keeping six feet of social distance.
Other scientists, however, have become increasingly concerned that the novel coronavirus spreads through a more insidious route—as an airborne pathogen. Every sneeze, cough, spoken word, or even exhaled breath expels droplets in a continuum of sizes. The worry is whether the tiniest— called aerosols—can harbor the SARS-CoV-2 virus and allow it to linger or float across a room, causing new infections.
In July, 239 scientists published a commentary in Clinical Infectious Diseases calling for the recognition of airborne transmission for COVID-19 based on a series of case reports and lab studies. Though debate remains over whether airborne coronavirus transmission happens outside of hospital settings, proponents say the public risks are too dire to wait for more research. They propose additions to health guidance, such as improving ventilation, and some are working on models to predict the hazards of this route of infection.
One example involves a pair of methods that have been used for decades to track pollutants in indoor spaces and the risk of infectious disease. The model can calculate risk for multiple scenarios—including a classroom, campus, subway, bus, choir, demonstration, and outdoors—allowing users to tweak a variety of variables, including the amount of mask wearing, group size, and activity. The results can provide a valuable comparison of relative risk, says Jose-Luis Jimenez, an atmospheric chemist at the University of Colorado Boulder who led the project. (Use this interactive model to measure the risk of airborne COVID-19 in your office, classroom, or bus ride.)