On September 18, CDC revised its guidelines to acknowledge that the “main way” the novel coronavirus (SARS-CoV-2) spreads is through aerosols. It also for the first time mentions that virus can spread through breathing, stay suspended in air and travel to distances beyond six feet.

In a major development, on September 18, the Atlanta-based Centers for Disease Control and Prevention (CDC) revised its guidelines to acknowledge that the “main way” the novel coronavirus (SARS-CoV-2) spreads is through aerosols.

The updated guidance says that the virus most commonly spreads through “respiratory droplets or small particles, such as those in aerosols, produced when an infected person coughs, sneezes, sings, talks, or breathes”. The CDC elaborates saying that these “particles can be inhaled into the nose, mouth, airways, and lungs and cause infection. This is thought to be the main way the virus spreads”.

Explaining the mechanism of virus spread, the revised guidelines reiterates that the virus may “spread through the droplets and airborne particles” that are formed when an infected person coughs, sneezes, sings, talks, or breathes. 

It also says that there is growing evidence that droplets and airborne particles can “remain suspended in the air” and be inhaled in by others. Most importantly, it clearly states that droplets and airborne particles can “travel distances beyond six feet (for example, during choir practice, in restaurants, or in fitness classes)”.

In cautions that in general, the risk of virus spread increases in indoor settings without good ventilation. The risk of spread increases when an infected person interacts more closely with others and the duration of such interaction is longer.

Previous CDC guideline

The last time the CDC revised its guidelines on virus spread was on July 16. Then, the CDC did not mention aerosols or airborne particles or about the likelihood of spread when a person breathes. It had only mentioned that the virus spreads from one person to another through respiratory droplets produced when an infected person coughs, sneezes or talks.

The World Health Organization had on July 9 acknowledged that novel coronavirus can be airborne in closed settings and spread from one person to another.

Now that both the WHO and CDC have acknowledged airborne spread of the virus and that the virus can spread to distances greater than six feet in certain settings, it is important to adopt universal masking especially in enclosed places with poor ventilation and to maintain physical distancing.

Published in The Hindu on September 21, 2020