SEATTLE -- Scientists studying tiny exhaled particles that could transmit the coronavirus say a Centers for Disease Control and Prevention decision to drop warnings against choral singing is dangerous, risking more "super-spreading events" such as a Washington state choir practice linked to two deaths.
The researchers say that the coronavirus can spread in respiratory aerosols, which may linger in the air for an hour or more, floating farther than the 6 feet commonly prescribed for social distancing. They say that choir members are particularly vulnerable to infection from airborne particles, because they exhale and inhale deeply to sing, often at close quarters in poorly ventilated rooms.
The CDC generally dismisses the potential for airborne transmission beyond 6 feet, although a study it published recently said the "act of singing" likely contributed to 53 of 61 people who attended a choir rehearsal in March getting sick, two of whom died of COVID-19. Since that incident north of Seattle, reports have surfaced of other outbreaks after choir performances, including one in Amsterdam that claimed four lives.
Without notice on its website May 23, the CDC altered guidance for reopening houses of worship, deleting a warning posted the previous day that said the act of singing may contribute to the transmission of COVID-19. The warning disappeared as President Donald Trump deemed religious institutions essential, calling on governors to reopen them from coronavirus lockdowns.
"Removing that guidance is extremely dangerous and irresponsible," said Jose Jimenez, a University of Colorado chemistry professor who studies aerosols, adding it "will put people at risk of additional super-spreading events and slow down the containment of the epidemic."
Donald Milton, a University of Maryland bio-aerosol researcher, spoke during a May 5 webinar sponsored by multiple national music organizations -- and since watched by more than 100,000 people -- that stunned the choir world. Experts advised choirs and performing arts groups not to gather again to sing in person until a vaccine or treatment for COVID-19 becomes widely available, even if that takes two years or more.
"The CDC's earlier recommendations were spot on, and I'm sorry to see that they've changed them," Milton said in an interview. "This is very hazardous, and we really need to not be getting together to sing."
The novel coronavirus surfaced only a little more than five months ago in Wuhan, China, therefore, some degree of uncertainty about the pathogen is to be expected, as scientists study its characteristics. But the conflicting advice from domestic and international health agencies is striking, creating confusion as the U.S. death toll continues rising above 100,000.
The White House, reported by The Washington Post as having directed the CDC to substitute approved guidance omitting the choir warning, declined comment. The CDC and the Department of Health and Human Services did not respond to interview requests.
Aerosols include tiny floating pieces of pollution that make up smog and dust particles visible wafting in rays of sunshine, said Shelly Miller, a University of Colorado professor of mechanical engineering. She said that a person coughing can throw 300,000 or more aerosols at speeds up to 60 mph, ranging from microscopic, at 0.7 microns, to the size of a grain of fine beach sand, at about 10 microns or more.