Aerosols likely pose the greatest danger in health care settings, but may also spread in some everyday scenarios.
Editor’s note: This article was updated on April 1 to reflect new evidence that aerosols may drive COVID-19 transmission beyond the context of heath care settings.
The study described in this article was published in The New England Journal of Medicine on March 17. This article was originally published on March 13.
The novel coronavirus SARS-CoV-2 can survive in the air for several hours in fine particles known as aerosols, according to preliminary research.
The coronavirus, which causes the respiratory infection COVID-19, can be detected up to 3 hours after aerosolization and can infect cells throughout that time period, the study authors found. However, the study, first posted March 10 on the preprint database medRxiv, is still preliminary, because it has not undergone extensive peer-review. The authors did receive comments from one prospective scientific journal, and posted an updated version of the study on March 13 reflecting the revisions.
Assuming these initial results hold up to scrutiny, aerosol transmission of SARS-CoV-2 appears “plausible,” the authors wrote — but several key questions remain unanswered.
“We still don’t know how high a concentration of viable SARS-CoV-2 is needed in practice to infect a human being, though this is something we are looking to model in the future,” co-author Dylan Morris, a graduate student in the Department of Ecology and Evolutionary Biology at Princeton University, told Live Science in an email. Morris and his colleagues tested whether viral particles from aerosols could infect cells grown in the lab, not actual human beings. More important, even if aerosol transmission can occur, it’s unlikely to be the primary force driving the current pandemic, Morris added.
At the time the study was published, the scientific consensus was “that most transmission via respiratory secretions happens in the form of large respiratory droplets … rather than small aerosols,” Morris said. “Droplets, fortunately, are heavy enough that they don’t travel very far” and instead fall from the air after traveling only a few feet.
Aerosols, by contrast, can potentially travel across far greater distances; the virus that causes chickenpox, for example, can travel tens of yards from an infected person and incite secondary infections elsewhere in the environment, and can remain in an area even after the person who emitted them has left. However, in the current study, the researchers did not examine how far SARS-CoV-2 could conceivably travel through the air.
Based on research on other respiratory viruses, Morris and his co-authors originally stated that aerosolized SARS-CoV-2 likely isn’t the primary driver of transmission in “everyday settings,” but could pose a danger in health care settings where specialized equipment is used. However, a recent account of members in a large choir group who tested positive for COVID-19 after rehearsal raises the possibility that aerosols may drive transmission beyond the bounds of a hospital.
“It’s now clear that aerosol risks are not negligible for everyday people, particularly in poorly-ventilated indoor areas,” Morris wrote in a tweet posted March 31. That said, hospital settings still carry a “particularly elevated risk for aerosol transmission” of SARS-CoV-2, he noted.
livescience.com / Balkantimes.press
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