Washington (AFP)

In the midst of an epidemic rebound, calls to impose a national obligation to wear a mask in the United States, in place of the current patchwork of rules, are strengthening, after multiple studies have demonstrated its effectiveness.

But while in Europe, countries are toughening their devices, US President Donald Trump refuses any new restrictions of national scope, relying instead on a future vaccine in the coming months.

He mocks his Democratic opponent, Joe Biden, whom he warns the Americans that he will want to reconfine them.

Mr. Biden supports a national mask obligation.

To date, 33 of the 50 American states have made the mask mandatory.

In the 17 others, cities have imposed here and there, locally, obligations ... Which opportunely created what the researchers call "natural experiments", making it possible to compare similar cities but which differ on the mask.

For example, in Kansas, the governor imposed the mask in July but the counties could obtain an exemption.

Only 20 of 105 counties have actually made the mask mandatory: transmissions there have been reduced by 50% compared to counties without obligation, according to researchers at the University of Kansas.

The problem with this method, also used in Texas or Oklahoma, is that it does not take into account the other health measures that often accompany the obligation of the mask, such as bar closures.

A study published in Health Affairs did so and concluded that the obligations imposed in the spring on the mask had, on their own, prevented between 230,000 and 400,000 cases in the United States as of May 22.

An epidemiological model from the University of Washington published recently in Nature even estimates that 130,000 deaths could be avoided by the end of February if 95% of the population wore a mask in the presence of other people.

- Large majority -

"Winter is coming: it's time for the mandatory mask," influential former head of the Drugs Agency Scott Gottlieb wrote in the Wall Street Journal on Sunday.

He pleads for a two-month obligation, and notes that "it is easier to wear a mask in winter than in summer".

Anthony Fauci, the country's chief infectious disease specialist, has been pleading for months for "low-tech" solutions against the epidemic: mask, physical distancing, seeing yourself outside rather than inside.

The subject is actually less controversial than what political debates or the constant misinformation spread on social media might suggest.

The vast majority of Americans already cover their faces: 78% in April and 89% in June said they do, according to a survey by the Centers for Disease Control (CDC).

Recent polls show similar numbers.

But when the virus is in an exponential dynamic, a minority is enough to make it last.

And do these 89% always wear the mask in stores, in restaurants between courses, in the car with a colleague ...?

Legally, the legality of a presidential decree imposing the mask everywhere in the country is not guaranteed either.

"Our legal team thinks I can do it, depending on the degree of crisis in the states," Joe Biden said in September, sounding less confident.

But the federal government has strong prerogatives in certain areas.

The CDC had prepared a directive in September to make the mask mandatory on planes, trains, buses, subways and airports - but the White House blocked it, according to the New York Times.

A new adviser to Mr. Trump on the pandemic, Scott Atlas, much disputed by the scientific and public health community, recently tweeted: "Do masks work? NO".

Twitter blocked the post.

The US federal government therefore remains the only one among the large countries to have completely delegated health measures to local levels, and that will not change for at least three more months.

Whatever happens to the November 3 election, Donald Trump will remain in power until January 20.

© 2020 AFP