Wearing masks to prevent coronavirus: here’s what scientists know


The CDC has been criticized for a flip-flop on masks since the start of the pandemic, when it urged only symptomatic people to wear them. The agency only recommended the universal use of face coverings in April. (The World Health Organization was even later, issuing its approval in July.)

The agency was reluctant to recommend masks at first because of concerns about a rush on the high-quality masks needed by healthcare workers, Dr Marr said. “I think it took a while to realize that there are different goals in the health setting versus the community,” she said.

It’s only natural when dealing with an unknown virus that recommendations change dramatically over time, Dr Wen said. “We know a lot more now, and I think we should admit that we were wrong,” she said.

Nonetheless, the changes in direction should be seen as a sign that the policy is following the latest science, she added.

“Somehow this change has been presented by some people as public health experts not knowing what we are doing,” said Dr Wen. “But in fact, we should see this shift in focus as part of the necessary evolution. It is the cornerstone of a strong public health response.

For example, it was not clear at first that the virus could be transmitted through the air, especially indoors and by people without symptoms. Scientists therefore speculated that the new coronavirus behaved like the coronaviruses responsible for SARS and MERS.

But the CDC was quick to recommend masks once it was clear asymptomatic transmission was a big contributor, Dr Brooks said: “Science is changing. So do we, and our recommendations too. “


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