The possibility that the coronavirus is lingering in the air could radically alter precautions countries are taking to contain it.
(CN) — The World Health Organization on Tuesday acknowledged there is emerging evidence the new coronavirus may be dangerously transmitted through the air in poorly ventilated indoor environments such as bars, churches, schools and meat factories.
In an open letter, a group of 239 scientists on Monday called on the United Nations health agency to warn people they may be at risk of infection when they are in closed spaces and are exposed to tiny airborne droplets containing the virus.
Their research suggests the virus may be emitted by people who are simply talking and that the virus may linger in the air inside poorly ventilated spaces for hours.
Until now, the WHO has said the virus is primarily transmitted when infected people emit relatively large droplets when they sneeze, cough and speak. But, contrary to the claims by the group of scientists, the WHO has said these droplets quickly sink and do not travel far. The health agency also warns that infection may occur when someone touches a surface where the virus has landed.
To avoid infection, the WHO has advocated maintaining distance from other people, frequent hand washing and wearing masks when it’s not possible to keep distant from other people.
This highly technical, but potentially crucial, debate was sparked after the New York Times published an article over the weekend about the scientists’ claims. Their findings, if found accurate, could radically alter precautions societies are taking to contain the virus. The scientists said the virus may not pose much of a threat when people are outdoors when winds and humidity disperse it.
During a news briefing Tuesday, the WHO’s experts said they were reviewing the evidence and will issue new guidelines soon. The agency’s experts said they had been debating the claims about airborne transmission since April. Scientists who provide WHO advice were among those signing the open letter.
“We acknowledge that there is emerging evidence in this field, as in all other fields, regarding the Covid-19 virus and pandemic,” said Benedetta Allegranzi, the WHO’s technical lead on infection control.
Allegranzi said the evidence about airborne transmission is “not definitive” but said the “possibility of airborne transmission in public settings, especially in very specific conditions, crowded, closed, poorly ventilated settings … cannot be ruled out.”
But she said “the evidence needs to be gathered and interpreted.”
“Therefore we believe that we have to be open to this evidence and understand its implications regarding the modes of transmission and also regarding the precautions that need to be taken,” she said.
Maria Van Kerkhove, the agency’s technical lead on Covid-19, said many of those signing the letter are engineers advocating for better ventilation. But she defended the WHO, saying it warned of airborne transmission.
“We have been talking about the possibility of airborne transmission and aerosol transmission as one of the modes of transmission of Covid-19,” she said.
The scientists warned that not enough attention is being paid to the threat of airborne infection.
“There is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (microdroplets) at short to medium distances (up to several meters, or room scale),” their letter states. (Parentheses in original.)
The scientists said viruses can be “released during exhalation, talking, and coughing” and can “remain aloft in air” where they can infect entire rooms.
They also cited studies of Covid-19 infections in China showing that airborne transmission was the most likely way people caught the infectious disease. The scientists also pointed to other cases involving widespread transmission at churches. One such outbreak took place in South Korea.
“This poses the risk that people sharing such environments can potentially inhale these viruses, resulting in infection and disease,” the letter states.
The scientists said the WHO does not recognize airborne transmission except in health care settings. They also said hand washing and social distancing are “insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people.”
To prevent transmission inside buildings, the scientists advocated better ventilation, minimizing the use of recirculating air, air filters and ultraviolet lights. They also said overcrowding in public transportation and public buildings should also be avoided.
The scientists said it is urgent to recognize the risk of airborne transmission “when countries are re-opening following lockdowns – bringing people back to workplaces and students back to schools, colleges, and universities.”
Also Tuesday, the world learned President Donald Trump has formally acted to withdraw the United States from the WHO over disagreements with its handling of the pandemic.
Trump announced his intentions in May, claiming the U.N. organization is controlled by China and did not adequately respond to the threat of coronavirus.
A spokesman for U.N. Secretary-General Antonio Guterres confirmed a notice of the U.S. withdrawal was delivered to the body Monday. Members of Congress received notification of the formal action Tuesday.
“It leaves Americans sick and America alone,” tweeted Senator Bob Menendez of New Jersey, the top Democrat on the Senate Foreign Relations Committee.
The withdrawal will not take effect for a year since a joint resolution passed by Congress in 1948 requires the U.S. to give the agency a year’s notice to leave.
Courthouse News reporter Cain Burdeau is based in the European Union.