Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder

Singing unmasked, indoors spreads COVID-19 through aerosols, new study confirms


Singing indoors, unmasked can swiftly spread COVID-19 via microscopic airborne particles known as aerosols, confirms a new peer-reviewed study of a March choir rehearsal which became one of the nation’s first superspreading events.

“This study documents in great detail that the only plausible explanation for this superspreading event was transmission by aerosols. Shared air is important because you can be inhaling what someone else exhaled even if they are far away from you,” said Shelly Miller, lead author on the study and professor of mechanical engineering. CIRES Fellow Jose-Luis Jimenez co-authored the work.

On March 10 in Skagit Valley, Washington, one person with mild symptoms of COVID-19 attended a 2.5-hour choir practice indoors. In the weeks that followed, more than 50 other people from that rehearsal would contract the disease—almost everyone who attended—and two died. Because participants had taken precautions to sanitize and avoid touching each other, scientists suspected that aerosol transmission, not larger drops spit into the air or infected surfaces, were the culprit. 

The new paper, published this week in the journal Indoor Air, confirms it. More...


CIRES is a partnership of NOAA and CU Boulder.


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