The World Health Organization (WHO) has underscored for months COVID-19 spreads mainly by direct contact with large respiratory droplets, like those expelled in cough or sneeze from a sick person. However, in a letter published in Clinical Infectious Diseases this week, 239 experts say the agency might be incorrect.
In a commentary aimed directly at the WHO for its reluctance to update its advice, researchers recommended new measures, including increasing indoor ventilation, installing high-grade air filters and UV lamps, and preventing building and transport overcrowding.
Is WHO really paying attention?
Experts from more than 30 countries argue the health authorities are not paying enough attention to airborne COVID-19 transmission. That is infection through inhaling tiny respiratory droplets that can linger in the air.
WHO officials acknowledged that possible transmission route at a press conference Tuesday, after the letter was published, but said it continues to collect evidence. "We have been talking about the possibility of airborne transmission and aerosol transmission as one of the modes of transmission of COVID-19," Maria Van Kerkhove, the WHO's technical lead for COVID-19, said.
Studies of other pre-pandemic viruses "demonstrated beyond reasonable doubt" that droplets released by people can stay on the air and pose a risk of exposure to an infected individual at distances beyond two meters. More recent evidence indicates the same is true for SARS-CoV-2, the COVID-19-causing virus. People have become sick in some reported cases after being in the same room as an infected individual, even if they have not had close or sustained contact.
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Think of the aerosols like cigarette smoke, says Linsey Marr, a Virginia Tech professor of civil and environmental engineering, and one signatory to the petition. The cloud is mostly focused around the smoking person, but it also disperses and drifts throughout the room. Viral aerosol functions precisely the same, she says.
The guidance of the WHO COVID-19 discussed airborne spread in healthcare environments, as some procedures that aerosolize the virus, but stopped short of calling it a threat to the public. However, the letter's 239 signatories say that's not good enough.
"There's been a lot of emphasis on hand-washing and on social distancing," Marr said. She suggested that the health organization provide additional guidance on ventilation techniques wearing masks whenever people congregate indoors if the WHO acknowledges that aerosol transmission is happening.
'Precautionary principle'
In response to the statement, the WHO said they are aware of the article, and their technical experts are reviewing its contents. Even the US CDC and its European counterpart are out of line with the WHO's guidance.
The authors agreed that microdroplet transmission was "admittedly incomplete," but said that large droplets and surface transmission were incomplete, but still formed the basis for safety recommendations.
"Following the precautionary principle, we must address every potentially important pathway to slow the spread of Covid-19," they wrote.
