Many experts said the W.H.O. should embrace what some called a “precautionary principle” and others called “needs and values” — the idea that even without definitive evidence, the agency should assume the worst of the virus, apply common sense and recommend the best protection possible.
“There is no incontrovertible proof that SARS-CoV-2 travels or is transmitted significantly by aerosols, but there is absolutely no evidence that it’s not,” said Dr. Trish Greenhalgh, a primary care doctor at the University of Oxford in Britain.
“So at the moment we have to make a decision in the face of uncertainty, and my goodness, it’s going to be a disastrous decision if we get it wrong,” she said. “So why not just mask up for a few weeks, just in case?”
After all, the W.H.O. seems willing to accept without much evidence the idea that the virus may be transmitted from surfaces, she and other researchers noted, even as other health agencies have stepped back emphasizing this route.
“I agree that fomite transmission is not directly demonstrated for this virus,” Dr. Allegranzi, the W.H.O.’s technical lead on infection control, said, referring to objects that may be infectious. “But it is well known that other coronaviruses and respiratory viruses are transmitted, and demonstrated to be transmitted, by contact with fomite.”
The agency also must consider the needs of all its member nations, including those with limited resources, and make sure its recommendations are tempered by “availability, feasibility, compliance, resource implications,” she said.
Aerosols may play some limited role in spreading the virus, said Dr. Paul Hunter, a member of the infection prevention committee and professor of medicine at the University of East Anglia in Britain.