Is the coronavirus transmitted more easily under certain climatic conditions? According to a study conducted by Predict Service, a subsidiary of Météo France, it is possible.

“The virus attaches itself to droplets. When it’s cold, they fall to the ground. When it’s hot, they evaporate. And in the middle, there are temperature and humidity conditions that are suitable for keeping these droplets in the air. So, if they are loaded with viruses, they can potentially transmit the disease more, ”explains Alix Roumagnac, president of Predict Service.

Pr Yves Buisson, epidemiologist at the head of the Covid cell of the Academy of Medicine, confirms this possibility: “We see that temperature, climate, solar radiation, air humidity, have an influence on the transmission. A particular hygrometry favors the aerosols, which stay longer in the air. “

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Epidemic peaks linked to certain climatic conditions

It all started with a study by MIT (Massachusetts Institute of Technology) in March 2020. According to this study, 90% of infections would have occurred in regions where climatic conditions are most conducive to the maintenance of droplets in the air. Namely, between 3 and 17 degrees Celsius and 35 to 85% humidity in the air, explains M Roumagnac.

The Predict team compared these climate data with data on contamination, hospitalizations and deaths due to Covid in France and around the world. “We observed that, where the climate was more conducive to the maintenance of droplets in the air, these data were the highest”, explains Alix Roumagnac.

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Several examples around the world

According to the president of Predict Service, a few days after the arrival of storm Alex in France, the country experienced a spike in hospitalizations and deaths linked to the second wave. In addition, “this summer, northern Europe came out of the first wave, while Australia, Argentina or South Africa were hit harder. “

The appearance of the epidemic in Wuhan could also be linked to the climate of the Chinese city, according to M Roumagnac. “In central China, the climate at the end of 2019 was very favorable to maintaining droplets in the air,” he explains. “In contrast, in Beijing for example, it was too cold for the droplets to stay in suspension. But when it is too cold, the pandemic does not develop. It could also explain why Northern Europe has long been more spared. “

Prof. Buisson shares this idea. According to him, “the flu, which is also a viral infection with respiratory transmission, is seasonal in temperate countries and the northern hemisphere. However, in the tropics, there is no influenza epidemic but quiet circulation, without an epidemic peak. This is also the case with this pandemic. “

“The climate is not a single factor”

However, this model is not sufficient to explain all the outbreaks of epidemics. Alix Roumagnac is well aware of this: “In Brazil, there was a peak of contamination in a climatic context which did not however favor it”, he recalls. In question in this country: “the density of population and the density of housing, especially in the poorest districts of the big cities”, explains Yves Buisson.

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“The climate is not a unique factor. The use of barrier measures remains essential ”, adds Alix Roumagnac.

Adapt your behavior

If epidemiologists confirm the results of Predict Service, Alix Roumagnac imagines a more dynamic management of the epidemic: “we can create measures according to the areas where the climate favors contamination the most. This indicator varies depending on the time of day, so you can also decide to go out when it is hotter rather than when it is colder and humid. “

According to Yves Buisson, this new study opens up other possibilities in the fight against Covid. “If we integrate the weather data into the epidemic models, it would perhaps be possible to say with a few days in advance ‘be careful, this week will meet all the conditions for there to be a very strong transmission’. This should make it possible to reinforce the containment or to take measures to limit the contamination.

“I believe that there must be close collaboration between meteorologists and epidemiologists responsible for modeling the epidemic,” adds the professor.

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The Covid will become “like a seasonal flu”

For Yves Buisson, humanity will not be able to eradicate the Covid. “It is a coronavirus, and those we know have a seasonal periodicity,” explains the professor. “When covid ceases to be a terrible pandemic, we will not be able to eradicate it, even after the vaccine campaign. “

This disease could become, like the flu, a seasonal epidemic. “As a large part of the world’s population will have been immunized, there will be small winter epidemics. It will be like the flu, a virus that is a little different each year, and we will adapt the vaccines. Knowing that coronaviruses mutate much less than influenza viruses, ”he explains.

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