Medical experts say the Center for Disease Control and Prevention’s statistic on the outdoor risk of coronavirus transmission is “misleading,” The New York Times reports.
The CDC announced last month that vaccinated people do not need to wear masks outdoors, citing a statistic that “less than 10 percent” of transmission occurs outdoors. That number has been parroted by media outlets but it “seems to be a huge exaggeration,” Dr. Muge Cevik, a virologist at the University of St. Andrews, told the Times.
Epidemiologists told the outlet that the actual rate of outdoor transmission is likely below 1% and quite likely as low as under 0.1%.
Some doctors say this is another example of the CDC’s struggles in public health communication. The agency continues to urge unvaccinated people to wear masks in most outdoor settings and recommends summer camps require children to wear masks virtually “at all times” despite the minimal risk of transmission.
“There is not a single documented Covid infection anywhere in the world from casual outdoor interactions, such as walking past someone on a street or eating at a nearby table,” the Times reported.
Many reports of outdoor transmission from Singapore:
An oversized share of reported cases of outdoor transmission are linked to construction sites in Singapore.
“In one study, 95 of 10,926 worldwide instances of transmission are classified as outdoors; all 95 are from Singapore construction sites. In another study, four of 103 instances are classified as outdoors; again, all four are from Singapore construction sites,” The Times explained, noting that the Singapore government database does not actually categorize these cases as outdoor transmission because they may have happened indoors.
But researchers had to choose one classification for construction sites and chose to label them all as outdoor. Yet, even those cases only amount to about 1% of the transmissions the studies found. Another study from Ireland with a more specific definition of outdoor found that the rate of such transmissions was actually below 0.1%.
Another study of more than 7,000 cases in China found just one instance of outdoor transmission.
“I’m sure it’s possible for transmission to occur outdoors in the right circumstances,” Dr. Aaron Richterman of the University of Pennsylvania told the Times, “but if we had to put a number on it, I would say much less than 1 percent.”
“There are limited data on outdoor transmission. The data we do have supports the hypothesis that the risk of outdoor transmission is low. 10 percent is a conservative estimate from a recent systematic review of peer-reviewed papers,” the agency said in a statement. “CDC cannot provide the specific risk level for every activity in every community and errs on the side of protection when it comes to recommending steps to protect health. It is important for people and communities to consider their own situations and risks and to take appropriate steps to protect their health.”