October 8, 2020

CDC Acknowledges Airborne Spread of SARS-CoV-2

Updated guidance on the CDC website states that the virus that causes COVID-19 can spread through exposure to small virus-containing respiratory droplets and particles that can remain suspended in the air over long distances and time periods. While acknowledging airborne transmission of SARS-CoV-2, the guidance maintains that most infections are spread through close contact.

Multiple news organizations have reported that language acknowledging airborne transmission of the virus was posted to the CDC website for a brief time in September before being removed.

“[W]ere SARS-CoV-2 spread primarily through airborne transmission like measles, experts would expect to have observed considerably more rapid global spread of infection in early 2020 and higher percentages of prior infection measured by serosurveys,” the guidance reads. “Available data indicate that SARS-CoV-2 has spread more like most other common respiratory viruses, primarily through respiratory droplet transmission within a short range (e.g., less than six feet). There is no evidence of efficient spread . . . to people far away or who enter a space hours after an infectious person was there.”

In July, the journal Clinical Infectious Diseases published a letter signed by more than 200 scientists calling for public organizations to address the potential for airborne spread of COVID-19. The letter acknowledges that evidence for airborne spread is “incomplete” but argues that other modes of transmission such as large droplets and fomites have similarly incomplete evidentiary support. “Following the precautionary principle, we must address every potentially important pathway to slow the spread of COVID-19,” the letter reads.

A similar letter published in Science on Oct. 5—the same date CDC updated its guidance—calls for “the balance of attention” regarding COVID-19 to “be shifted to protecting against airborne transmission.”