CU Study Confirms Singing Unmasked Inside Spreads COVID Through Particles

BOULDER, Colo. (CBS4) - A new study done by University of Colorado scientists confirms that singing without a mask on inside can spread COVID-19 particles easily. The study examined a March rehearsal in Washington.

The study, which has been peer reviewed and published in the journal Indoor Air, proves that aerosols projected by singing unmasked spreads the virus. Researchers studied a choir rehearsal in Skagit Valley, Washington, on March 10. One person with mild COVID-19 symptoms attended the 2-and-a-half hour indoor rehearsal. In the weeks that followed, nearly everyone who attended the practice -- more than 50 people -- contracted the disease. Two people ultimately died.

Those who attended had sanitized surfaces and avoided touching each other. That observation led scientists to conclude that particles spit into the air during the singing spread the disease.

No one in attendance was wearing a mask.

Researchers interviewed a chorale representative and calculated the rate of infection based on details of the rehearsal and known facts about the SARS-CoV-2 virus. Scientists concluded that there was not a large enough window for droplets and infected surfaces to transmit the number of people who contracted the disease. However, poor ventilation in the practice space did lead to what researchers called a "build-up of aerosols produced by the singers themselves mixed the air within the room."

"The inhalation of infectious respiratory aerosol from 'shared air' was the leading mode of transmission," Jose-Luis Jimenez, co-author of the study, professor of chemistry and fellow at the Cooperative Institute for Research in Environmental Sciences, said.

The infection rate in the practice was 87%, or 52 people. Researchers found that shortening the practice to 30 minutes would have dropped that infected rate to 12%, or 5 people.

Before that event, there were known cases in Skagit County. Other superspreader events related to choir practices have been recorded in the Netherlands, Austria, Canada, Germany, England, South Korea, Spain, and France.

"The research adds to the overwhelming body of evidence that aerosol transmission is playing a major role in driving this pandemic and especially to superspreading events," Jimenez said.