The CDC Revises COVID-19 Transmission Guidelines to Include Airborne Particles

The Centers for Disease Control (CDC) revised its guidelines for preventing transmission of the Coronavirus on Friday, now saying that it can be spread by aerosols and large droplets saying the virus primarily spreads by air: through droplets or other tiny respiratory particles that apparently can remain suspended and inhaled.

The smaller particles, known as aerosols, are produced when an infected person coughs, sneezes, sings, talks or breathes and can be inhaled into someone’s nose, mouth, airways or lungs, according to the CDC, which says that, in general, indoor settings without good ventilation increase the risk of contagion.

The Washington Post reported that although the CDC updated its guidance to mention aerosols on Friday, it was not widely noticed until CNN reported on it Sunday.

“This is thought to be the main way the virus spreads,” the CDC posted on its website. “There is growing evidence that droplets and airborne particles can remain suspended in the air and be breathed in by others and travel distances beyond six feet (for example, during choir practice, in restaurants or in fitness classes).”

Experts on aerosols and the coronavirus said the change constitutes a profound shift in understanding of how the virus that has claimed almost 200,000 lives in the United States spreads. However, the updated two-page explanation provided little new guidance on how to protect against airborne transmission.

The new CDC guidance is important because cloth masks aren’t designed to protect the wearer from aerosols.

The World Health Organization publicly addressed the threat of aerosols in July at the urging of hundreds of scientists, and according to the Post, it’s unclear why the CDC is following suit months later.

According to the Los Angeles Times, “The CDC and the World Health Organization have long resisted the notion that the coronavirus spreads farther than about six feet through the air, with the WHO initially maintaining that airborne transmission occurred only during certain medical procedures. But in July, under growing pressure from researchers, the WHO acknowledged that the virus could linger in the air indoors and potentially infect people even when they practice social distancing. Aerosol scientists have found mounting evidence — including “super-spreading” events such as choir practices in which multiple people were infected — that the virus can spread through microscopic respiratory particles. This week, the scientific journal Indoor Air accepted a paper for publication that found that many of the 53 choir singers who became sick after attending a March 10 practice in Mount Vernon, Wash., likely caught COVID-19 through airborne transmission.”

The CDC highlights in its new guidance: “Airborne viruses, including COVID-19, are among the most contagious and easily spread. Some viruses are highly contagious, like measles, while other viruses do not spread as easily. The virus that causes COVID-19 appears to spread more efficiently than influenza, but not as efficiently as measles, which is highly contagious. In general, the more closely a person with COVID-19 interacts with others and the longer that interaction, the higher the risk of COVID-19 spread.”