Coronavirus: why it is too early to say that the peak of contamination is behind us

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Coronavirus: the deadly epidemic that worries the planet

VIRUS – Has the worst of the coronavirus epidemic passed? While the WHO has indicated this weekend that the number of cases of affected people is stabilizing in China, Éric Leroy, member of the National Academy of Medicine, sheds light on us.

While the coronavirus epidemic has already affected more than 40,000 Chinese people and caused nearly 1,000 deaths, has the peak of contamination already been reached? According to the World Health Organization (WHO), the number of people affected is stabilizing (Sunday, just over 3,000 new cases were identified in China). “We are recording a period of stability, where the number of reported cases has not increased,” rejoiced this weekend Michael Ryan, head of WHO’s emergency health programs.

However, it is too early to say that the peak of contamination has been reached, according to Eric Leroy, director of research at the Research Institute for Development and member of the National Academy of Medicine. “According to estimates, the peak would have been calculated around the month of February. Some say it was the 8th, some speak of this week, others of the next … So we would be at the peak. But that is not a certainty, “tempers the researcher at LCI. “For the moment, these are only estimates based on parameters taken into account at the very beginning of the epidemic, and which are not fixed,” he continued before developing his remarks.

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Another source of contamination than Wuhan?

“A lot of things come into play,” continues Éric Leroy. “The calculations are based on an algorithm, which takes many parameters into account. The problem is that they can change as the epidemic unfolds,” he said. “If there is a change in the measures taken, this will necessarily have an influence on the development of the epidemic and therefore on its peak, which can occur before or after.”

Another unknown: the number of foci of contamination. “Currently, the epidemic is spreading from a primary focus, which is in Wuhan City, from an animal source. But perhaps there is another animal source more or less far which may be the source of a second home, “worries the researcher. Wuhan residents may also have left town before the epidemic began, and spread the virus elsewhere. “These are elements that we do not control”. These unknowns could therefore distort estimates of the course of the epidemic.

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Will the weather affect the spread of the virus?

But they are not alone. “A respiratory virus is highly dependent on climate, seasons, humidity, cold, heat,” said the researcher. The weather could therefore play its role in the evolution of the epidemic. But again, it is unpredictable. “Depending on the climate, there can either be an increase in the spread of the virus, or a decrease. A humid climate, with a lot of water vapor in the atmosphere, propels the viral particles down,” and therefore strengthens the epidemic.

The virus itself is also difficult to grasp. “A virus mutates a lot, and it’s a difficult parameter to take into account,” said the specialist. “Depending on the number of people affected and the difference in the number of people affected, the virus can evolve more or less quickly. Mutations are a bit of a coincidence, we cannot predict them at the start. So there is a set factors that are taken into account in the algorithm, but which are themselves scalable. And it is difficult to say whether or not the peak has already been reached. “

Finally, it is also possible that the number of cases in Southeast Asia is still underestimated. “In rich countries, where there is a health system that allows diagnoses, we know the precise situation”, explains Professor Olivier Schwartz, head of the “virus and immunity” unit at the Pasteur Institute, at the microphone of TF1, in the video at the head of this article. “But in some countries where diagnoses are not made, or less efficiently, we do not know” the exact number of cases, he concludes.

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