WHO reviewing stance on masks in light of droplets from coughs can reach 6m and sneezes 8m

BBC published a report today (‘Coronavirus: Expert panel to assess face mask use by public‘, 2 Apr) saying that a panel of advisers to the World Health Organization (WHO) are now weighing to decide if masks should be recommended to be worn by people.
It came after new research in US shows that the COVID-19 virus can travel further than previously thought. The study suggests that droplets from coughs can reach as far as 6m and from sneezes up to 8m.
The panel’s chair, Prof David Heymann, who is the former director at WHO, told BBC that the new research may lead to a shift in advice about masks. Prof Heymann explained, “The WHO is opening up its discussion again looking at the new evidence to see whether or not there should be a change in the way it’s recommending masks should be used.”
Presently, WHO advises that healthy people only need to wear masks if they are caring for others suspected of being infected or if they themselves are coughing or sneezing.
The new research conducted at the Massachusetts Institute of Technology (MIT) used high-speed cameras and other sensors to assess precisely what happens after a cough or sneeze. Researchers found that an exhalation generates a small fast-moving cloud of gas that can contain droplets of liquid of varying sizes – and that the smallest of these can be carried in the cloud over long distances. It found that coughs can project liquid up to 6m away and that sneezes, which involve much higher speeds, can reach up to 8m away.
The scientist who led the study, Prof Lydia Bourouiba of MIT, said that she is concerned about the current concept of “safe distances”. She said, “What we exhale, cough or sneeze is a gas cloud that has high momentum that can go far, traps the drops of all sizes in it and carries them through the room.”
“So having this false idea of safety at one to two metres, that somehow drops will just fall to the ground at that distance is not based on what we have quantified, measured and visualised directly,” she added.
Prof Bourouiba’s view is that in certain situations, especially indoors in poorly ventilated rooms, wearing masks would reduce the risks.
“Flimsy masks are not going to protect from inhaling the smallest particulates in the air because they do not provide filtration,” she said. “But they would potentially divert the cloud that is being emitted with high momentum to the side instead of forward.”
Commenting on the study, Prof Heymann, said that if the evidence is supported, then “it might be that wearing a mask is equally as effective or more effective than distancing.”
But he adds a warning that masks need to be worn properly, with a seal over the nose. If they become moist, he explained, then particles can pass through. People must remove them carefully to avoid their hands becoming contaminated.
The WHO’s panel, known as the Strategic and Technical Advisory Group for Infectious Hazards, is due to hold its next virtual meeting in the next few days.

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