Coronavirus Is Aerosolized Through Talking, Exhalation, New Report Says

Alicia Ault

April 04, 2020

Editor's note: Find the latest COVID-19 news and guidance in Medscape's  Coronavirus Resource Center.

An expert committee has concluded that the novel coronavirus is aerosolized through talking or exhalation, but it's not yet clear if the viral particles are viable and emitted in doses sufficient to cause infection.

"While the current SARS-CoV-2 specific research is limited, the results of available studies are consistent with aerosolization of virus from normal breathing," wrote Harvey Fineberg, MD, PhD, chair of the National Academies Standing Committee on Emerging Infectious Diseases and 21st Century Health Threats, in a rapid expert consultation issued April 2.

Although aerosolization could be considered a third potential route of transmission — along with large droplets emitted from sneezing or coughing and the transfer of viral particles after touching a contaminated surface — the relative contribution of each mode is uncertain, Fineberg told Medscape Medical News.

It's also still unclear what it takes to cause infection through aerosolization, he said.

"The best approach without that clear description is all three are possible and we have to guard against all three," he said.

Asked if there is any risk to operating on the assumption that the novel coronavirus can be transmitted through aerosols, Fineberg said, "I see no downside at this time at all." 

But, he said, that assumption does not change what he thinks are the best precautions in healthcare facilities, which include handwashing and wearing of personal protective equipment (PPE). Although N95 masks provide the greatest measure of protection, it's not realistic to expect that they can be worn by all personnel, said Fineberg.

"This is a question of prioritization, of risk, and of availability," he said. In addition, N95s are difficult to wear for extended periods of time and may not be necessary in every circumstance, said Fineberg, citing a gradient of risk.

The committee looked into the issue of aerosolization at the request of the White House Office of Science and Technology Policy (OSTP), Fineberg said.

The report cited several studies it said supported the idea that SARS-CoV-2 is airborne. One study (still in preprint and not yet peer reviewed) by Joshua Santarpia, PhD, and colleagues at the University of Nebraska Medical Center in Omaha, has gotten a lot of attention. The researchers collected air and surface samples from 11 rooms of patients with COVID-19, and found viral RNA in the air both inside and outside the rooms and on ventilation grates.

Another study in preprint looking at hospitals and public areas in Wuhan found that the highest concentrations of virus were in toilet facilities and in PPE removal rooms. Doffing of the PPE may potentially have aerosolized the virus, the researchers hypothesized.

Fineberg and colleagues, however, approached the finding with caution, stating that "it may be difficult to re-suspend particles of a respirable size." More likely, "fomites could be transmitted to hands, mouth, nose, or eyes without requiring direct respiration into the lungs," they write.

The report did not cite a recent overview in the Journal of the American Medical Association by Lydia Bourouiba, PhD, of the Massachusetts Institute of Technology in Cambridge. The report noted that recent research has found that "exhalations, sneezes, and coughs not only consist of mucosalivary droplets following short-range semiballistic emission trajectories but, importantly, are primarily made of a multiphase turbulent gas (a puff) cloud that entrains ambient air and traps and carries within it clusters of droplets with a continuum of droplet sizes."

She said that the lifetime of a droplet could be extended "from a fraction of a second to minutes," and that the cloud carrying viral particles could travel as far as 23 to 27 ft (7-8 m).

The World Health Organization (WHO) still contends (in a report dated March 29) that current evidence shows that "COVID-19 virus is primarily transmitted between people through respiratory droplets and contact routes," and that it can only become airborne during procedures or treatments that generate aerosols.

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