Ventilate and wear the mask indoors: these barrier gestures are more important than ever at a time when the Covid-19 epidemic is restarting, according to a study by the Pasteur Institute on the expansion of the Delta variant in France this summer, published Friday, November 26 in the medical journal The Lancet Regional Health Europe (in English).
Unsurprisingly, the most risky places for contamination were poorly ventilated enclosed spaces: evenings to watch Euro football matches at home or in bars, nightclubs or, to a lesser extent, transport, which does not was not the case with previous variants, presumably because Delta is more transmissible.
“The practical consequence is to remember the importance of ventilation and wearing a mask”, specifies to AFP the head of the study, the epidemiologist Arnaud Fontanet. This is all the more true as Europe is currently experiencing a “epidemic relaunch synchronous with a cold wave” which pushes people to stay indoors, and therefore more at risk, he adds.
This part of the Institut Pasteur study covers the period from May 23 to August 13, which corresponds to the gradual reopening of public places after the third confinement and the appearance of the Delta variant on the territory.
No additional risk was identified during this period for the restaurants, which reopened on May 19 outdoors and June 9 indoors. It is “probably because it was the height of summer and we could open the windows wide and put people on the terrace”, note Arnaud Fontanet.
Widely documented in numerous studies, the increased risk in poorly ventilated areas comes from the fact that SARS-CoV-2 is transmitted overwhelmingly via aerosols, those clouds of particles that we emit when we breathe (and even more so when we breathe). let’s talk, shout or sing).
Despite this, the importance of aeration (which disperses these clouds, like cigarette smoke) is not always well understood by the general public. “We weren’t clear enough about ventilation, we scientists” admits Arnaud Fontanet, member of the Scientific Council which guides the French government. “Just an open door indoors on a corridor, in a classroom for example, it is already something, even if it is better to open a window”, he insists.
This part of the study is based on data from 12,634 people who tested positive between May 23 and August 13, and 5,560 uninfected controls. All the people answered a detailed questionnaire to determine the risk of contamination according to the places frequented.