Scientists in the United States government believe that the new coronavirus is probably transmitted by people when they speak and breathe. Logical consequence: Americans are now officially advised to cover their faces outside their homes, to help curb contagions.
President Donald Trump announced it on Friday evening, insisting that it was a recommendation, not mandatory. The health authorities call on the population to cover their faces with handmade masks, scarves or bandanas, in order to reserve medical masks for carers, a shortage means.
In New York, the mayor had already asked residents to cover their faces outside their homes, and as of Friday, just under half of pedestrians were applying the order in Manhattan, according to an observation by AFP journalists.
Seen from Asia, where surgical masks are omnipresent, the delay in Western countries is an aberration. But health authorities in the United States or France, as well as the World Health Organization, have argued so far that the mask is not necessary for healthy people, unless they are in contact with the sick.
For several days, a flip-flop had been preparing, under pressure from an audience that did not understand why the masks would protect nurses but not ordinary citizens.
In France, the Academy of Medicine recommended Friday the compulsory wearing of the mask, as a “logical addition to the barrier measures”.
In the United States, on Friday, the director of the Institute of Infectious Diseases, Anthony Fauci, a member of the White House working group on the coronavirus who says he spends an hour a day with President Trump, spoke on Fox News of evidence that “the virus can actually be transmitted when people are just talking, rather than just when they sneeze or cough”.
Airborne transmission would provide a long-sought explanation for the apparent high contagiousness of the virus responsible for the Covid-19 pandemic, since it appears that infected but symptomless people, who account for perhaps a quarter of all infected people , are responsible for a large part of the contagions, without their knowledge.
Multiple studies have shown that asymptomatic people have infected people close to them in churches, in a choir or a singing class, in retirement homes …
Some studies
What is the scientific evidence? There are few, but they converge.
The American Academies of Sciences cited in a letter to the White House Wednesday four studies tipping the balance in favor of transmission of the virus via the air exhaled by people (“aerosols” in scientific jargon), and no longer only by the droplets and postlets projected during a sneeze directly on the face of other people or on surfaces (where the virus can survive for hours or even days, depending on the type of surface).
“The research currently available supports the possibility that SARS-CoV-2 can be transmitted by bioaerosols generated directly by the exhalation of patients,” writes Harvey Fineberg, chair of the committee on emerging infectious diseases.
He points out that more is needed to better understand the real risk of infection. If the virus is actually present in respiration, it is not known whether this represents a significant route of transmission quantitatively.
In a study, researchers from the University of Nebraska found portions of the genetic code for the virus (RNA) in the air of rooms where patients were isolated.
Researchers at the University of Hong Kong recently observed that wearing masks reduced the amount of coronavirus exhaled by patients (the experiment was done with viruses other than SARS-CoV-2).
And researchers in Wuhan took air samples from various hospital rooms and found high concentrations of the new coronavirus, especially in the toilets and rooms where caregivers removed their protective gear.
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