July 16, 2020

WHO Considers Potential of Airborne Transmission of SARS-CoV-2 in Indoor Settings

A scientific brief published earlier this month by the World Health Organization states that WHO is evaluating whether SARS-CoV-2 may spread through aerosols in indoor settings. According to the brief, some reports of outbreaks related to crowded indoor spaces have suggested the possibility of aerosol transmission combined with droplet transmission. These reports have come from outside of medical settings—for example, during choir practice, in restaurants, and in fitness classes.

“In these events, short-range aerosol transmission, particularly in specific indoor locations, such as crowded and inadequately ventilated spaces over a prolonged period of time with infected persons cannot be ruled out,” WHO’s brief explains. “However, the detailed investigations of these clusters suggest that droplet and fomite transmission could also explain human-to-human transmission within these clusters.”

The organization states that further studies are needed to determine what role aerosols might play in transmission in these types of settings.

WHO’s scientific brief incorporates additional new evidence available on the transmission of SARS-CoV-2. The brief was published a few days after an open letter from more than 200 scientists in Clinical Infectious Diseases urged public health organizations like WHO to address the potential for airborne spread of COVID-19.

“Studies by the signatories and other scientists have demonstrated beyond any reasonable doubt that viruses are released during exhalation, talking, and coughing in microdroplets small enough to remain aloft in air and pose a risk of exposure at distances beyond 1 to 2 [meters] from an infected individual,” the letter says. “For example, at typical indoor air velocities, a 5 µm droplet will travel tens of meters, much greater than the scale of a typical room, while settling from a height of 1.5 m to the floor.”

WHO’s new brief maintains that SARS-CoV-2 is predominately spread through direct, indirect, or close contact with infected people.