WHO Says COVID-19 May Be Lingering in the Air; Knox County Health Department Awaits Further Evidence
The World Health Organization has formally acknowledged COVID-19 may be transmitted by lingering in the air, not just through large respiratory droplets. But what the new guidance will mean in Knox County is yet to be determined.
Hundreds of studies have been published since the start of the pandemic about how SARS-CoV-2, or the virus that causes COVID-19, is transmitted. But 239 leading scientists around the world came together with one common finding last week – COVID-19 could be airborne.
In a letter published by Clinical Infectious Diseases, the scientists – many of whom consult the WHO – appealed public health agencies to recognize the possibility of airborne spread of COVID-19, citing studies about other types of coronaviruses and unexplained COVID transmission events.
Airborne diseases refer to those you can catch by breathing alone, as opposed to ones that are spread by large droplets that enter the body through eyes, nose or mouth. Classification as airborne applies to some of the world's most contagious diseases, like mumps and measles. The newest guidance acknowledges that COVID-19 could be lingering in the air in tiny droplets called aerosols, possibly for hours.
“Some people define airborne as happening at very long distances, and I would say that might be happening but we don't know yet … But I am 100% sure that transmission is occurring by inhalation of virus in aerosols,” Dr. Linsey Marr, who helped write the letter, said.
Scientists already know that some coronaviruses, like ones that cause the common cold, are transmitted through tiny, airborne droplets. Marr says this is compelling evidence COVID can linger in the air too, and that it’s the best explanation for some of the things that have happened during this pandemic.
“There have been laboratory studies showing that the virus can remain infectious in aerosols for many hours and we also have seen these super-spreading events, for example, the choir in Washington state and a restaurant in China,” Marr said. “I'm sure there are many others, but these are the ones where we have the most evidence. The only reasonable explanation is that the virus spread by inhalation of aerosols or microdroplets.”
Following the scientists’ letter, the World Health Organization added guidance about avoiding enclosed spaces with poor ventilation and acknowledged the possibility of airborne transmission but did not definitively say the virus is being transmitted by tiny, airborne particles. They’ve maintained that close, personal contact is the main transmission method.
“Short-range aerosol transmission, particularly in specific indoor locations, such as crowded and inadequately ventilated spaces over a prolonged period of time with infected persons cannot be ruled out,” the updated scientific brief says.
But while the extent of airborne spread of COVID is still in question at public health agencies, scientists agree on one thing – wearing a mask slows the spread. This is what the Knox County Health Department has focused on in response to the latest science. Charity Menefee is in charge of emergency preparedness for the health department.
“We are eager to see what consensus comes from all the emerging evidence and information that’s coming from the scientific community. I think the practical guidance for the community is still the same: wearing a face covering is very important,” Menefee said. “It just reiterates and re-emphasizes the need to do that.”
Dr. Linsey Marr, who studies infectious disease transmission at Virginia Tech, agrees that airborne virus particles make mask-wearing even more important but would like to see guidelines about wearing facial coverings even at distances greater than six feet. She also said more attention should be paid to ventilation.
“There's a couple of additional things to do; which is to avoid crowded indoor spaces, and to make sure that our indoor spaces, these rooms and buildings, have good ventilation with enough outdoor air coming in rather than just recirculated air,” Marr said.
If COVID-causing virus particles are floating in the air, inadequate ventilation is especially concerning in crowded places like schools and jails. Right now, Knox County is following the Tennessee Pledge which recommends, but doesn’t mandate, opening doors and windows for air circulation. The county’s mask mandate in place only applies when 6 feet of distance can’t be maintained. The director of the Knox County Health Department, Martha Buchanan, says she’s waiting for more proof of airborne transmission to recommend changes.
“I think there’s still a lot more to learn about this virus. If the science does prove that it is airborne that will change things. Right now, what we know for sure is that its droplet spread, you have to have close proximity to the person to get it,” Buchanan said. “We’re learning more about this virus and we’ll have to see if more evidence comes out and tells us something different.”