The Coronavirus Can Float in Indoor Air, W.H.O. Concedes

The coronavirus may linger in the air in crowded indoor spaces, spreading from one person to the next, the World Health Organization formally conceded on Thursday.

The W.H.O. had described this form of transmission as rare and possibly insignificant. But growing scientific and anecdotal evidence suggest 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 W.H.O. 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.