"It's the calm before the storm": can we control the variants of Covid-19?

“I hope I'm wrong and the epidemiologists I know, but I'm afraid it will be the calm before the storm.

"Like Pascal Crépey, professor-researcher in epidemiology at the School of Advanced Studies in Public Health, caution dominates within the scientific community, while France escapes confinement and its curve of positive cases remains flat.

Since January 23, between 20,000 and 20,500 people have tested positive for Covid-19 each day, if we smooth the data over a week to erase the daily variations.

A quasi-stability which is opposed to the increase of 13% during the ten previous days.

It is again and again the variants that arouse the concern of specialists in the modeling of the epidemic.

Optical illusion"

The good news, largely put into perspective by 300 deaths per day in hospital and more than 3,000 people in intensive care, concerns the "flat" dynamics of the epidemic, which seems to confirm the effects of an advanced curfew generalized to 18 hours, announced Jan. 14.

"The stability of the cases indicates that relatively strict measures are taken, with controls," explains Renaud Piarroux, epidemiologist and head of the parasitology department at the Pitié-Salpêtrière hospital.

If we only had the initial strain, which remains in the majority, we would note a certain effectiveness;

the curve would even be declining slightly each week.

"

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The doctor, however, evokes "a kind of trompe-l'oeil": "On the other hand, the number of cases of variants is increasing by 50% per week.

We started from very low to reach 2,000 daily cases, soon to be 3,000. Over time, the new strain will take on an increasingly large proportion.

"

These progress statistics are those unveiled by the Minister of Health Olivier Véran last Thursday.

This Tuesday, Rémi Salomon, president of the medical commission of the Public Assistance-Hospitals of Paris (AP-HP) indicated that the latest results were "not good" in Ile-de-France, with 15 to 20% of English variants.

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Pascal Crépey also fears "a drop, then suddenly a strong rise", according to the same mechanism: "We must consider that we have two different epidemics today, with distinct reproduction rates.

We have a plateau or a decline because the measures are effective on the first variant (

Editor's note: the version of the virus known since last winter

), but perhaps not enough for the second (

Editor's note: the English version

) ”.

Tens of thousands of cases in early March?

For "forecasters", nothing in the latest studies allows us to envisage a lasting stabilization on this "high plateau" of 20,000 cases, or even a gradual descent.

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"We are sure that the dreaded phenomenon is occurring, since the number of variants is increasing exponentially," describes Professor Piarroux.

A month ago, we did not know that they were there, on January 7 we were at about 3% of 20,000 cases, or 600 per day, today we have reached several thousand.

This shows that the variant manages to progress strongly despite the measures.

As long as the old strain remains in the majority, we keep this stability, but the more frequent the variant becomes, the more it will print its rhythm.

"

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A quick calculation makes it possible to project the rise in power of the English variant if it pursues an identical dynamic.

By multiplying by 1.5 the number of daily cases of VOC202012 / 01 each week, we can estimate that the "mutant" alone will cross the daily bar of 20,000 cases in early March.

"Once at 20,000 cases per week, the next one you add 10,000 additional cases (

Editor's note: 30,000 variant cases in total

), then 15,000 the one after (

Editor's note: 45,000 cases

) ... on this second part that things change more quickly and become quite dramatic, ”explains Pascal Crépey.

The Rennes epidemiologist urges us not to wait to fight against the spread, collectively or individually: “The fire is smoldering.

But its spread is not inexorable, because this variant is transmitted like the current virus.

We just need more strong, better monitored and more effective measures.

It depends on political decisions, but also on individual behavior.

There is no need for the government to decree lockdown today to limit its contacts.

"

Renaud Piarroux also believes that it will soon - again - be necessary to tighten the screw: “Whether we call it confinement or something else, the problem is to close the current places of transmission, in particular high schools, colleges and perhaps be the schools.

"