CDC changes, then retracts, its take on coronavirus spread

The top U.S. public health agency has stirred confusion by posting — and then taking down — an apparent change in its position on how easily the coronavirus can spread from person to person on small droplets in the air.

Officials at the Centers for Disease Control and Prevention say the virus spreads primarily through small airborne droplets, like those that fly through the air when someone coughs or sneezes. Most CDC guidance about social distancing is built around that idea, saying that 6 feet is a safe buffer between people who are not wearing masks.

In interviews, CDC officials have also acknowledged growing evidence that the virus can in some cases also spread via even smaller, aerosolized particles or droplets that spread over a wider area. That’s one of the reasons public health experts stress wearing a mask, which can stop or reduce contact with both larger droplets and aerosolized particles.

The CDC has maintained that the spread is mainly through the larger droplets. And for months the website said little about aerosolized particles. So the agency's position appeared to have changed when the CDC on Friday quietly posted an update that discussed aerosolized particles in more detail. The post added singing and breathing to the ways the virus can go airborne, and said the coronavirus can remain suspended in the air and drift more than 6 feet. It also emphasized the importance of ventilation indoors.

Federal health officials on Monday said the posting Friday was a mistake, put out before full editing and clearance was completed. They said the CDC is planning to clarify the agency's thinking, but it did not immediately release a statement or revision.

The agency has come under attack for past revisions of guidance during the pandemic, some of which were driven by political considerations by the Trump administration.

Some said that whatever drove the most recent confusion, the episode may further chip away public confidence in the CDC.

“The consistent inconsistency in this administration’s guidance on COVID-19 has severely compromised the nation’s trust in our public health agencies, "said Dr. Howard Koh, a Harvard University public health professor who was a high-ranked official in the U.S. Department of Health and Human Services during the Obama administration.

“To rectify the latest challenge, the CDC must acknowledge that growing scientific evidence indicates the importance of airborne transmission through aerosols, making mask wearing even more critical as we head into the difficult fall and winter season,” Koh said in a statement.