The coronavirus can float in indoor air, WHO concedes
Geneva, Jul 10: The coronavirus may linger in the air in crowded indoor spaces, spreading from one person to the next, the World Health Organization formally conceded Thursday.
The WHO had described this form of transmission as rare and possibly insignificant. But growing scientific and anecdotal evidence suggests this route may be important in spreading the virus, and this week more than 200 scientists urged the agency to revisit the research and revise its position.
In updated guidance documents, the agency also acknowledged unequivocally for the first time that the virus can be spread by people who do not have symptoms: "Infected people can transmit the virus both when they have symptoms and when they don't have symptoms," the agency said.
The WHO previously said asymptomatic transmission, while it may occur, was probably "very rare."
Some experts said both revisions were long overdue and not as extensive as they had hoped.
"It is refreshing to see that WHO is now acknowledging that airborne transmission may occur, although it is clear that the evidence must clear a higher bar for this route compared to others," said Linsey Marr, an aerosol expert at Virginia Tech.
An aerosol is a respiratory droplet so small it may linger in the air. In its latest description of how the virus is spread, the agency said transmission of the virus by aerosols may have been responsible for "outbreaks of COVID-19 reported in some closed settings, such as restaurants, nightclubs, places of worship or places of work where people may be shouting, talking or singing."
The WHO had maintained that airborne spread is only a concern when health care workers are engaged in certain medical procedures that produce aerosols. But mounting evidence has suggested that in crowded indoor spaces, the virus can stay aloft for hours and infect others, and may even seed so-called superspreader events.
The agency still largely emphasizes the role played by larger droplets that are coughed or inhaled, or by contact with a contaminated surface, also called a fomite. And the WHO still maintained that "detailed investigations of these clusters suggest that droplet and fomite transmission could also explain human-to-human transmission."
In addition to avoiding close contact with infected people and washing hands, people should "avoid crowded places, close-contact settings, and confined and enclosed spaces with poor ventilation," the agency said.
-The New York Times Company