According to some scientists, airborne transmission is the most likely explanation for multiple infection groups, including a choir in Washington State and a restaurant in China.
However, WHO staff have not yet accepted the importance of these case studies, and instead have “made up an alternate story” in which an infected person spat on his hands, wiped them on something, and numerous other people, Dr. Greenhalgh, said “magically” infected.
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The agency’s staff and almost 30 volunteer experts spent weeks checking evidence of possible transmission routes: by exhaling large and small droplets, for example by contact with a contaminated surface or from a mother to her baby.
WHO easily accepts that droplets and fomite are transmitted, but appears to want more accurate evidence of aerosol spread, some experts said. The agency found that, for example, the virus was not cultured from air samples, but the same was true for influenza for many years until two groups of scientists figured out how to do it, said Don Milton, an aerosol expert at the University of Maryland.
WHO officials are reluctant to make statements unless they have irrefutable evidence of certain phenomena and are slow to update their hypotheses, scientists have accused. “They are still challenged by the lack of evidence and the difficulty of proving a negative,” said Dr. Hanage.
“The WHO is overly cautious and unnecessarily short-sighted,” said Dr. Julian W. Tang, honorary professor of respiratory science at the University of Leicester in the UK, in an email.
“By recognizing SARS-CoV-2 aerosol transmission and recommending the improvement or installation of improved ventilation systems, you can improve human health” by eliminating a variety of hazards, including indoor pollutants and allergens.
“Isn’t that what WHO stands for – improving human health from every angle?”