There has been a flurry of recent news stories about aerosol spread of COVID-19. This has been prompted predominantly by an open letter from 600 scientists criticizing the WHO and Centers for Disease control for not emphasizing the risk of aerosol spread of SARS-CoV-2.
The major routes of COVID-19 spread, according to the U.S. Centers for Disease Control and Prevention and the World Health Organization, is by respiratory droplets from someone who is coughing, sneezing or even talking within a few feet of another individual. I have previously argued that given this is a respiratory virus, the emphasis should be on wearing masks to prevent the spread of droplets and not on surface disinfectants.
The strongest scientific evidence supporting airborne transmission of COVID-19 comes from a study published in Nature. In this report, researchers measured viral RNA in aerosols from two hospitals in Wuhan, China, the city where the pandemic began. This analysis surveyed air samples from different parts of the hospitals and showed the SARS-CoV-2 genetic material (and presumably the virus itself) in air from wards, clinics and even bathrooms.
In addition, several “super spreader” events have reinforced the possibility of aerosol spread, including a choir practice in Washington State in early March and an episode in an air-conditioned restaurant in China in late January. In both these episodes people not in contact with the infected individual became sickened with the virus. This suggested the virus spread widely as a mist through the air. A good review of this issue is presented in a recent article from Scientific American.
There does not seem to be a lot of argument about this concept, but I provide several important notes on this topic. It is not surprising these aerosols occur and are most likely to be present indoors, where wind and sunlight cannot disrupt them. They are significant mainly with medical procedures that generate aerosols and with indoor crowds, where people are talking, singing or otherwise expelling virus. Most importantly, wearing masks can prevent the spread of COVID-19 through aerosols, just as with respiratory droplet transmission that is already recognized by the WHO and CDC. So if you wear your mask, COVID-19 aerosols should be no addition concern!