After months of mounting evidence that the coronavirus can be spread by air, the US Centres for Disease Control and Prevention (CDC) has updated its guidelines to recognize that the coronavirus can be airborne.
According to the CDC, the guidelines were updated because of the growing evidence that individuals with COVID-19 can infect people from over six feet away or after the infected person has left the area. Such cases often occurred in poorly ventilated and enclosed spaces, and often involved activities that cause heavier breathing, including singing or exercise. “The 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 said in a statement.
Earlier in September, the CDC had already published guidance recognizing the airborne transmission; however, this information was retracted. In July, numerous health experts addressed an open letter to the World Health Organization (WHO) in July calling for the organization to acknowledge this mode of COVID-19 transmission. However, the WHO still has not acknowledged airborne transmission as one of the main reasons of the rapid propagation of the virus, while many aerosol researchers spoke out against CDC’s reluctance to recognize this mode of transmission for the coronavirus. The CDC maintains that airborne transmission of COVID-19 occurs only in “limited, uncommon” circumstances. Over the course of the pandemic, airborne transmission has been a topic of widespread debate due to its potential impact on the regulation of public spaces including schools, restaurants and bars, gyms and offices.
“The thing people need to understand is aerosol transmission is like everyone breathing out cigarette smoke, and you want to breathe in as little of others’ as possible. Everyone you are around, imagine they are breathing smoke, and try to avoid it,” said Jose-Luis Jimenez, an aerosol expert from the University of Colorado told MIT Technology Review in an interview.
Under the new guidelines, CDC advises to keep a distance of at least six feet away from other individuals, as well as to wear a mask that covers the nose, and frequent hand washing, sterilization of surfaces and staying home when feeling sick.
According to some health experts, CDC should take the guidelines one step further to recommend proper building ventilation practices, as well as limiting the number of people indoors and encouraging people to carry out social activities outside.
Jimenez has criticized the new CDC update for its potentially confusing wording, with the term “small droplets” used instead of the widely accepted word “aerosols.” Jimenez also said the guideline diminishes the significance of airborne transmission. “We know that super-spreading events are a major component of transmission. And every single super-spreading event that has been studied appears to be dominated by aerosol transmission,” he said. Jimenez also said that the CDC update suggests airborne transmission from sharing a room together is rare, while it is actually a common way of transmission.