239 Experts alert the World Health Organization: The Coronavirus Is Airborne https://www.nytimes.com/2020/07/04/health/239-experts-with-1-big-claim-the-coronavirus-is-airborne.html?smid=tw-share

The World Health Organization has long held that the coronavirus is spread primarily by large respiratory droplets that, once expelled by infected people in coughs and sneezes, fall quickly to the floor.

But in an open letter to the WHO, 239 scientists in 32 countries outlined the evidence showing that smaller particles can infect people, and are calling for the agency to revise its recommendations. The researchers plan to publish their letter in a scientific journal next week.

Dr. Benedetta Allegranzi, the WHO’s technical lead on infection control, said evidence for the virus spreading by air was unconvincing. "[W]e consider airborne transmission as possible but certainly not supported by solid or even clear evidence,” she said.

“There is a strong debate on this.”

But interviews with nearly 20 scientists — including a dozen W.H.O. consultants and several members of the committee that crafted the guidance —

— and internal emails paint a picture of an organization that, despite good intentions, is out of step with science.

In early April, a group of 36 experts on air quality and aerosols urged the W.H.O. to consider the growing evidence on airborne transmission of the coronavirus.

The agency responded promptly, calling Lidia Morawska, the group’s leader and a longtime W.H.O. consultant, to arrange a meeting.

But the discussion was dominated by a few experts who are staunch supporters of handwashing and felt it must be emphasized over aerosols, according to some participants, and the committee’s advice remained unchanged.

They said the W.H.O. was making an artificial distinction between tiny aerosols and larger droplets, even though infected people produce both.

“We’ve known since 1946 that coughing and talking generate aerosols,” said Linsey Marr, an expert in airborne transmission of viruses at Virginia Tech.

Dr. Marr and others said the coronavirus seemed to be most infectious when people were in prolonged contact at close range, especially indoors, and even more so in superspreader events — exactly what scientists would expect from aerosol transmission.