Micro-droplets of infectious coronavirus could be airborne for hours and social distancing practices may not be enough to stop infection and spread, experts said.
In an open letter to the international science community, 239 health experts urge their colleagues to take airborne transmission seriously as COVID-19 cases rise in most parts of the USA.
Though most of the heavier respiratory droplets don’t reach more than 6 feet from a person, aerosolized droplets can span an entire room and hang in the air for several hours, according to the letter published July 6 in the journal Clinical Infectious Diseases.
“There is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (micro-droplets) at short to medium distances (up to several meters, or room scale), and we are advocating for the use of preventive measures to mitigate this route of airborne transmission,” experts wrote.
The World Health Organization doesn’t recognize aerosolized transmission except in health care settings through “aerosol-generating procedures.” The Centers for Disease Control and Prevention said “airborne transmission from person-to-person over long distances is unlikely.”
The open letter argues airborne transmission could be the only plausible explanation behind super spreader events where social distancing protocols were followed to prevent respiratory droplet transmission, as chronicled in an early Chinese study.
In other studies, researchers found viral RNA in these micro-droplets but were unable to prove that they could infect a healthy person. Dr. Matthew Heinz, hospitalist at Tucson Medical Center in Arizona, said there’s plenty of anecdotal evidence to suggest airborne transmissible is possible.
“I think that it is true that we don’t have a complete picture in terms of evidence as whether they’re confirmed to be infectious,” he said. “But on the front lines … it seems (airborne transmission) is happening based on who I’m admitting and their described behavior.”
If airborne transmission plays a big role in the spread, the country may have to rethink many of its prevention methods. Heinz said this could include increasing social distancing from 6 feet to 15 or 20 feet, changing air flow management and canceling inside activities.
“Even crowded together outside in an open-air situation is still a problem,” Heinz said. “We really need to be more cautious upfront.”
Frank Esper, a physician at the Cleveland Clinic Children’s Center for Pediatric Infectious Diseases, said it’s not only impractical to impose such stringent measures but also unnecessary as social distancing practices have already reduced transmission.
Though he doesn’t doubt airborne micro-droplets may contribute to the spread, he said respiratory droplets are the main mode of transmission.
“Am I surprised that aerosolization is one component of the virus spread? No,” he said. “Obviously, we want transmission to be zero, but we still really need to focus on what are the major modes of spread from person to person and place to place.”
The WHO and CDC need more evidence to definitively declare airborne transmission as a major driver before rewriting recommendations, and Esper said there are studies that seek to answer that question. He argued public health agencies need to soften their stance on aerosolized transmission.
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In the open letter, scientists recommend taking the following measures to mitigate airborne transmission risk:
Provide sufficient and effective ventilation by supplying clean outdoor air and minimizing recirculating air in public buildings, office, schools, hospitals and nursing homes.
Supplement general ventilation with airborne infection controls such as exhaust, high-efficiency air filtration and germicidal ultraviolet lights.
Avoid overcrowding, particularly in public transport and buildings.
"No one is saying this is playing the entire role, but what the scientists are trying to say is that we need to pay more attention in preparation for resurging cases that we expect to occur in the months to come," Esper said.
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.
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This article originally appeared on USA TODAY: COVID-19: Coronavirus spreads by airborne transmission, experts say