Paris (AFP)

Better a homemade mask than no mask at all: despite the lack of scientific certainty, this is what doctors advise the general public, not to protect yourself from the coronavirus but to avoid contaminating others.

"This is an important point: many people think that wearing a mask protects them from contamination, while it actually reduces the sources of transmission," said Professor KK Cheng, a public health specialist, to AFP. at the University of Birmingham (England).

"It works if everyone is wearing one, and in this case, a very basic mask is enough, because a piece of cloth can block the projections" of contaminated salivary droplets emitted by a patient, he adds. "It's not perfect, but it's much better than nothing."

Professor Cheng considers this collective protection all the more important since in the case of the coronavirus, everyone can be contagious without knowing it: "We do not know the proportion, but patients transmit the virus even without symptoms".

However, there is no scientific certainty in terms of effectiveness.

"It is unclear whether homemade masks would reduce transmission, there has been very little research on it," said Prof Benjamin Cowling, epidemiologist at the University of Hong Kong, to AFP.

In 2013, a Cambridge University study concluded that in the event of an influenza pandemic, "homemade masks should only be used as a last resort" but "they are better than no protection".

And even the doctors who recommend them insist that this should not obscure barrier measures, such as hand washing.

- Shortage -

Since the start of the epidemic, many western countries have reiterated that the widespread use of masks is not necessary. A position which, seen from Asia, surprised.

"The big mistake in the United States and Europe, in my opinion, is that people don't wear masks," the head of the Chinese Center for Disease Control and Prevention Gao Fu said on Friday. interview with Science magazine.

"Putting on a mask is not in Western culture," analyzes Professor Cheng, according to whom another parameter may have played: the fear that an official recommendation would lead the general public to throw themselves on the masks reserved for caregivers ( surgical masks and more protective masks because they are filtering, called FFP2).

"If people think that you wear a mask to protect yourself, it can lead to a shortage," said Professor Cheng.

"There is a glaring lack of surgical masks, and nobody wanted to involve the population by saying + We are not able to equip you, equip yourself +", adds the pulmonologist Nicolas Hutt, who practices in Alsace, one of the French regions most affected.

He too calls on the population to wear "alternative masks, craft or produced by industries" other than medical, while the lack of masks for caregivers has caused controversy in France.

- "Screens" -

"These are not masks for medical purposes, but rather anti-postillon screens for the general public", said the French doctor to AFP, advocating their use "in all areas where measures of distancing are not properly followed, like shops. "

Tutorials for making handmade masks are widely circulating on the internet, sometimes from hospitals. In France, the Standardization Association (Afnor), attached to the Ministry of Industry, posted a user manual on Friday.

In recent days, several European countries have posted a new position on the wearing of masks. It is compulsory in the Czech Republic and Slovenia, and Austria announced Monday that it wanted to generalize it in supermarkets.

Saturday, during a long press conference to take stock of the epidemic, French Prime Minister Edouard Philippe said he was "well aware of this important sensitivity to the question of masks".

The French authorities have been saying for several weeks that you do not need masks if you are not sick. However, the head of government announced that companies specializing in "textiles and paper" would be encouraged to "create new masks" for "very specific uses".

They will be intended for "all those who, not being medical personnel (...), will be able to find with guaranteed masks a good way of equipping themselves, reassuring themselves, protecting themselves and fighting against the epidemic".

Some could even be signed by big names in luxury: Chanel said on Saturday that it wanted to produce "first protection masks (...) as soon as the prototypes and raw materials have been approved".

© 2020 AFP