PARIS — Mum’s the word (to help stop the spread of the virus).

France’s Académie Nationale de Médecine (National Academy of Medicine) is urging people using public transportation to keep quiet on subways, buses and trains — whenever social distancing is not possible to achieve.

“The mandatory wearing of masks on public transport, where social distancing is not possible, should be accompanied by one very simple precaution: avoid talking and making phone calls,” the academy said Friday in a statement.

Masks have been mandatory on public transportation across the country since May.

On Saturday, academy member Patrick Berche told BFM TV that there’s no problem if there are only two or three people in a subway car, but when people stand close to each other, it makes sense not to talk — either in person or on the phone.

But he added that “it is not an obligation, it is a recommendation.”

The academy’s recommendation comes as new, more contagious variants of the virus begin to spread around the globe.

“According to the WHO, these two [variants of the coronavirus — one first found in the U.K., the other in South Africa] quickly spread around the world, reaching 60 and 23 countries and territories respectively, including France,” doctors said, adding that “the circulation of more contagious variants in the population is likely to worsen the current epidemiological situation.”

Founded in 1820, the National Academy of Medicine was instituted to “respond to the requests of the government on everything that concerns public health, and mainly on epidemics, diseases...the spread of vaccines,” according to its original mission.

The academy is not an official advisory body. It responds to government questions and also issues recommendations — which could sometimes go against official government policy, according to Reuters.