Unlike the French strategy, which seeks to find contact cases, the retrospective method known as "Japanese-style" targets the person who has infected a patient.

A method that has proven itself in Asia.

This is one of the axes of the government's strategy to fight the coronavirus: tracing.

The stated objective of the method is to find the contact cases of a patient to break the chains of contamination and,

ultimately

, to undermine the circulation of Covid-19 in France.

But there is another method to achieve this result: retrospective tracing, a method used in Asia and especially in Japan.  

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Find who to infect who

Unlike "classic" tracing, here the objective is to go back to patient zero: to find not the contact cases of a patient, but by whom the latter was contaminated.

By extension, this strategy therefore makes it possible to identify the important places of contamination.

"It's a bit like looking for the ascendants instead of looking for the descendants", summarizes at the microphone of Europe 1 epidemiologist Catherine Hill.

A strategy widely used in Asia, much more spared from the virus than the Old Continent.

"It's done remarkably well in South Korea, but they did it right and they tested a lot."

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"We have never watched well enough"

"They isolated a lot and the virus circulated a lot less. So they know very well who infected whom? And who infected 230 people, for example. We have never monitored well enough."

"Whenever we can go beyond the chain of contamination, we do it", defended for his part the Minister of Health Olivier Véran, questioned on this question.

"But don't think that this is something you just have to snap your fingers and put in the means."

And to qualify: "There are answers that we do not manage to have, but that no one in the world manages to obtain, whatever the strategy."

However, regardless of the tracing strategy used, one point is consensus in the scientific community: it is impossible to correctly trace the epidemic beyond 5,000 cases per day.

However, according to the latest figures from Public Health France published on Sunday, France had more than 52,000 new cases detected in 24 hours.