After hundreds of experts urged the World Health Organization to review growing scientific research, the agency acknowledged on Tuesday that aerial transmission of the coronavirus could be a threat in indoor spaces.
WHO expert committees are examining the evidence for transmission of the virus and plan to release updated recommendations in a few days, agency scientists said in a press briefing.
The possibility of airborne transmission, particularly in “crowded, closed and poorly ventilated places, cannot be excluded,” said Dr. Benedetta Allegranzi, who heads the WHO committee on infection prevention and control. .
She said the agency recommends “adequate and optimal ventilation” of indoor environments, as well as physical distance.
Agency staff responded to several questions from journalists about the transmission of the virus by air, following an open letter from 239 experts calling on the agency to review its guidelines. Many signatories to the letter have collaborated with WHO and served on its committees.
Experts who signed the letter welcomed the WHO announcement.
“We are very pleased that WHO has finally recognized the accumulated evidence and will add indoor aerosol transmission to probable modes of transmission” for the coronavirus, said Jose-Luis Jimenez, professor of chemistry at the University of Colorado to Boulder. “This will allow the world to better protect themselves and fight the pandemic.”
In their letter, Dr. Jimenez and other scientists called on the WHO to recommend that people avoid overcrowding, especially on public transport and other confined spaces. Public buildings, businesses, schools, hospitals and nursing homes should also provide clean air, minimize air recirculation, and consider adding air filters and anti-virus UV lamps. they declared.
“Public health agencies around the world are drawing inspiration from WHO, and I hope that this will lead to more emphasis on wearing face covers and avoiding the three Cs: close contact, closed spaces and poorly ventilated and crowded, “said Linsey Marr, an aerosol expert at Virginia Tech. “These measures will help slow the pandemic and save lives.”
WHO scientists have said that in recent months the infection prevention committee has evaluated the evidence for all the ways in which the coronavirus is spread, including by tiny droplets or aerosols.
“We recognize that there is emerging evidence in this area, as in all other areas,” said Dr Allegranzi. “And therefore, we think we need to be open to this evidence and understand its implications for modes of transmission and the precautions to be taken.”
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It will also be important to understand the importance of aerosol transmission compared to larger droplets and the dose of virus needed for aerosol infection, she said.
“These are areas that are growing and for which evidence is emerging, but it is not final,” she said. “However, the evidence must be gathered and interpreted, and we continue to support this.”
Other experts said it had been clear for some time that aerial transmission of the virus was possible, but agreed that he was not yet certain of the extent of the role played by this route in the spread of the virus. virus.
“The question of its importance for global transmission remains open,” said Bill Hanage, epidemiologist at the Harvard TH Chan School of Public Health.
Yet he and other experts have said that the WHO is too slow and cautious in adopting precautions based on emerging evidence.
WHO scientists explained their seemingly slow pace. On average, they review 500 new articles per day, many of which are of questionable quality, said Dr. Soumya Swaminathan, WHO chief scientist.
As such, scientists must examine the quality of each article before including it in their analysis, she said, “Any advice we offer has implications for billions of people around the world.” It must be done with care. “