"Reduce from 40,000 to 5,000 contaminations".
This is the goal set by Emmanuel Macron, "in the long term", by announcing Wednesday evening a new containment of all metropolitan France from Friday.
"It is only then that we will be able to redeploy a
Test, Alert, Protect
strategy
", continued the Head of State.
This October 28, the daily number of new cases is precisely 39,673, on average over the past week (the figure for Monday is still very low because many labs are closed on weekends).
And the curve took two months to climb from the 5,000 threshold reached on August 30.
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So when can we expect a division by eight?
For the President of the Scientific Council, it is unthinkable within a month, the expected date of this reconfinement for the moment.
"On December 1, we will not be at 5,000 contaminations per day, I can tell you straight away," Jean-François Delfraissy said this Thursday morning on RTL, anticipating at least a curfew encompassing the Christmas period.
"It is totally illusory to hope for it on December 1, all the people who do modeling will tell you," adds the Parisian Jean-Stéphane Dhersin, deputy scientific director at the CNRS and specialist in the modeling of epidemics.
Two weeks to see the effect of confinement
And this, especially since the curve of new cases is expected to rise further in the coming days.
The effects of the confinement that starts this Friday will not be observable for at least two weeks, and those of the 9 p.m. curfew in effect since last Saturday in 54 departments do not seem convincing.
"By running the mathematical model with the figures available today, we should go up to [a peak of] 70,000 new cases in two weeks", indicates Stéphane Dhersin.
If the containment measures are well respected, the modeler estimates that we could approach the level of 5000 in mid-December, at the earliest.
This hoped-for and expected decrease in contamination will depend on the evolution of the reproduction number “R”, that is to say on the number of people that an infected individual will infect on average.
It is this indicator, less general public, which makes it possible to "guide" the curve of new cases.
As long as it is above 1, it means that the epidemic is progressing and the number of contaminations is increasing.
"It doesn't take much to achieve this"
This "R" is now at 1.42, according to the latest data available.
It is, of course, much less than at the start of the first wave (nearly 3), in particular thanks to the barrier gestures and the massively respected wearing of the mask, but we had returned to the value 1 at the end of September.
"The objective is to go back as quickly as possible below 1, we have the impression that not much is enough to achieve it", estimates the epidemiologist Carole Dufouil, who does not imagine, she does not plus, reach 5,000 new contaminations before the end of the year.
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Note that we cannot be based on the "first wave" of the epidemic to have an idea of the time frame to divide the number of new cases by eight.
Indeed, this indicator was largely underestimated at the time because we tested very few people.
Fortunately, it will not necessarily be essential to reach this threshold of 5,000 new cases to ease the re-containment.
"If the drop in R is very marked, we can imagine revising the conditions of confinement before," anticipates Carole Dufouil.
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