WHO acknowledges coronavirus can spread via airborne particles

The World Health Organization, under pressure from scientists, acknowledged Thursday that the coronavirus can spread via airborne transmission indoors, underscoring the difficulty public health experts are having in analyzing the mysterious virus.

The WHO had said in March that airborne transmission could be possible in certain circumstances, but the organization has emphasized that droplets people forcefully expel through sneezing or coughing are prime spreaders.

“Airborne transmission of the virus can occur in health care settings where specific medical procedures, called aerosol generating procedures, generate very small droplets called aerosols,” the global health group said in the new brief.

The shift came as public health officials grapple with how to combat the virus, which has infected more than 12.1 million people around the globe and has led to more than 550,000 deaths.

The virus is continuing to rage across the South and West in the United States. There are now more than 3 million cases in the country and more than 132,000 deaths.

The WHO stopped short of explicitly confirming that the virus spreads through the air but said more studies on the matter are “urgently” needed.

“To the best of our understanding, the virus is primarily spread through contact and respiratory droplets,” the study said.

The brief pointed to some reports, connected to crowded spaces indoors, that have suggested a combination of aerosol and droplet transmission “for example, during choir practice, in restaurants or in fitness classes.”

More than 200 scientists recently wrote an open letter to the global health agency to try to get it to update its stance on the issue of airborne transmission.

Their letter said studies have demonstrated “beyond any reasonable doubt” that viruses are released when people breathe, talk or cough droplets that are small enough to remain in the air and pose a danger to others even beyond a 6-foot distance.

Lidia Morawska, a professor at the Queensland University of Technology in Australia who helped spearhead the letter, said she had mixed feelings about the WHO’s brief.

Ms. Morawska said it was a “big step forward” for airborne transmission to be included in the recommendations but that the WHO’s analysis doesn’t pass muster as a “science based document.”

“Much more work is needed and I am hoping that WHO is open to accept help in bringing the recommendations in line with science, and most importantly to expand on the [measures] needed to control airborne transmission,” she said.

Dr. Donald Milton, a University of Maryland professor and the other lead author of the letter, said the WHO’s statement was “a move in the right direction” but that aspects of the organization’s brief were concerning.

For example, the group is suggesting that face masks are recommended only when within 1 meter, or 3 feet, of someone else.

“Recommending masks only within one meter is not supported by the science,” Dr. Milton said.

He did say he appreciated recommendations that people should avoid enclosed spaces with poor ventilation and that ensuring good ventilation in indoor spaces such as homes and offices is recommended.

Dr. Amesh A. Adalja, a senior scholar at the Johns Hopkins Center for Health Security, said the brief probably isn’t enough for researchers to drastically change the view that airborne transmissions are possible but aren’t necessarily widespread.

“Does speech and coughing and sneezing in an ordinary situation result in the infection of other people through airborne transmission? The WHO is still saying that there’s still not enough data to say that definitively,” Dr. Adalja said. “It’s not impossible, but it hasn’t been proven or certain.”

The WHO has been under fire for its response to the global pandemic, and the White House officially notified the United Nations and Congress this week that it was withdrawing from the group.

President Trump and others have criticized the WHO for too eagerly accepting the narrative from China, where the virus was first discovered late last year, on the scope and origin of the virus.

The WHO said in its March brief that in an analysis of more than 75,000 COVID-19 cases in China, airborne transmission was not reported.

But a study published in early April in concert with the Centers for Disease Control and Prevention found that 10 people who had eaten in the same air-conditioned restaurant in Guangzhou, China, all ended up infected.

The study concluded that the most likely cause of the outbreak was droplet transmission and that “strong airflow” from the air conditioner could have moved droplets from table to table.

“Virus-laden small aerosolized droplets can remain in the air and travel long distances” greater than 1 meter, the study said.

The group did say in the new brief that fabric masks can serve as a barrier to droplets being expelled into the air.

The WHO had resisted recommending that the general public wear face masks as a preventative measure until early June.

The group had said earlier in the year that people who weren’t sick or caring for others should avoid wearing masks to keep the supplies available for frontline health workers.

That advice was in line with what the federal government was telling people in the U.S. early in the year before the CDC issued new guidance in early April saying people should wear masks when in public.

Now, health officials in the Trump administration are trying to hammer home the point that people should be wearing face coverings when it’s not possible to practice social distancing.