Microdroplets of infectious coronavirus could be airborne for hours and current social distancing practices may not be enough to stop infection and spread, experts argue.
In an open letter to appeal to the international science community, 239 health experts urge their colleagues to take airborne transmission seriously as COVID-19 cases continue to rise in the most parts of the United States.
While most of the heavier respiratory droplets don’t reach more than six feet from a person, aerosolized droplets can span across 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 (microdroplets) 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 healthcare settings through “aerosol-generating procedures.” The Centers for Disease Control and Prevention have 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 have found viral RNA in these microdroplets but were unable to prove that they can infect a healthy person. Dr. Matthew Heinz, hospitalist at Tucson Medical Center in Arizona, says 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 spread, the country may have to rethink many of its prevention methods. Heinz said this could include increasing social distancing from six 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.”
Dr. Frank Esper, a physician at the Cleveland Clinic Children’s Center for Pediatric Infectious Diseases, believes it’s not only impractical to impose such stringent measures but also unnecessary as current social distancing practices have already proven to reduce transmission.
While he doesn’t doubt airborne microdroplets may contribute to spread, he believes respiratory droplets are still 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 to person to person and place to place.”
The WHO and CDC need more evidence to definitively declare airborne transmission as a major driver of spread before rewriting recommendations and Esper said there are studies in progress that seek to answer that question. However, he argues these public health agencies also 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 local 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 int he months to come,” Esper said.
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