A study raises questions about how far droplets, like those that carry the virus that causes COVID-19, can travel before becoming harmless

RICHLAND, Wash.—A modeling study raises questions about how far respiratory droplets, like those that transmit the virus that causes COVID-19, can travel before becoming harmless. Can the airborne particles that carry the virus remain infectious not just for a few feet but rather more than 200 feet, farther than the length of a hockey rink?

Experiments dating to the 1930s proposed two paths for respiratory droplets like those from a sneeze or cough. Either they are big and heavy, plummeting to the ground without much chance of infecting another person. Or they are so small and light that they dry out almost instantly, remaining airborne but becoming harmless very quickly. The dryness renders “enveloped” viruses like coronaviruses unable to infect.

But a new study from scientists at the Department of Energy’s Pacific Northwest National Laboratory suggests a third option—that small respiratory particles can remain moist and airborne for a longer time and greater distance than scientists have recognized.

“There are reports of people becoming infected with a coronavirus downwind of an infected person or in a room several minutes after an infected person has exited that room,” said Leonard Pease, the corresponding author of the study. The findings were published in the February issue of the journal International Communications in Heat and Mass Transfer.

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