CDC Officially Acknowledges Airborne Transmission of Coronavirus

“Today, CDC issued updated guidance to its How COVID-19 Spreads website, which includes information about the potential for airborne spread of the virus that causes COVID-19,” the agency wrote Monday in a press release.

By doing so, the CDC is finally catching up with what many health experts have been warning for months, NPR pointed out. The World Health Organization acknowledged airborne transmission in July after 239 scientists wrote a letter urging the organization to take airborne spread seriously. The U.S. agency seemed ready to accept airborne transmission last month, when it posted guidance saying that COVID-19 was most commonly spread “through respiratory droplets or small particles, such as those in aerosols,” as CBS News reported at the time. However, it quickly removed the update, saying it was draft language posted in error.

Monday’s updated guidance admits to airborne transmission once again, but says it is not the most common way the coronavirus spreads.

“CDC continues to believe, based on current science, that people are more likely to become infected the longer and closer they are to a person with COVID-19,” the agency wrote in the press release announcing the change. “Today’s update acknowledges the existence of some published reports showing limited, uncommon circumstances where people with COVID-19 infected others who were more than 6 feet away or shortly after the COVID-19-positive person left an area. In these instances, transmission occurred in poorly ventilated and enclosed spaces that often involved activities that caused heavier breathing, like singing or exercise. Such environments and activities may contribute to the buildup of virus-carrying particles.”

In the updated guidance, the CDC compared the airborne transmission of COVID-19 to the spread of other diseases like tuberculosis and chicken pox.

Outside scientists were pleased with the change.

“It’s gratifying to see CDC acknowledge that there’s a role for airborne transmission with this virus,” University of Maryland aerobiologist Donald Milton told NPR.

Milton co-wrote a letter in Science Monday urging clearer public health communication around airborne transmission of the new coronavirus. Unlike the CDC, Milton and his colleagues think that COVID-19 is primarily airborne, even when spread between people in close contact with one another.

In the letter, they differentiate between virus spread via droplets, which are larger and tend to fall to the ground, and virus spread via aerosols, which are smaller and remain aloft.

“Individuals with COVID-19, many of whom have no symptoms, release thousands of virus-laden aerosols and far fewer droplets when breathing and talking. Thus, one is far more likely to inhale aerosols than be sprayed by a droplet, and so the balance of attention must be shifted to protecting against airborne transmission,” they wrote. “In addition to existing mandates of mask-wearing, social distancing, and hygiene efforts, we urge public health officials to add clear guidance about the importance of moving activities outdoors, improving indoor air using ventilation and filtration, and improving protection for high-risk workers.”

In its list of preventative measures, the CDC does call for avoiding crowded indoor spaces and making sure indoor spaces are properly ventilated, as well as for spending time outdoors or in well-ventilated spaces as much as possible.

The CDC also recommends staying six feet apart from others, wearing masks, washing hands and surfaces frequently and self-isolating if sick.