how to explain the epidemic rebound?

Reference is made to the infectiousness of the BA.2 subvariant, but also to the relaxation of barrier gestures in the population.

A slight increase in positive Covid-19 cases has been noted in recent days, raising fears of a new spike in infection and an increase in hospital admissions, while in France almost all health restrictions have been lifted. The obligation to wear a face mask in closed indoor spaces was thus lifted on Monday.

“We are currently seeing a revival, in France, in the countries around us, that is, the Covid virus is no longer declining, it is actually increasing,” said Health Minister Olivier Véran on Friday.

“The lifting of the measures does not mean the end of the epidemic, the epidemic is very present, the infections are unfortunately starting to rise again and it is quite inevitable,” emphasizes Yves Coppieters, medical epidemiologist and professor of public law. health, this Monday on BFMTV. But “the impact on hospital indicators is currently very low”.

The more contagious BA.2 subvariant

“What explains today’s recovery? It is a BA.2 subvariant of Omicron that is more contagious than its predecessor and is in fact causing this increase in the epidemic,” said epidemiologist Arnaud Fontanet this Monday on France Inter

“The Scientific Council, which I have asked for, tells us that it is mainly the BA.2 subvariant that is at the root of this” epidemic revival, Prime Minister Jean Castex had already explained on Saturday in the Parisian† “It’s more transmissible than the original Omicron, but it doesn’t appear to be more dangerous,” he said, trusting that “the pressure in the hospital, which remains our justice of the peace, continues to fall.”

According to the latest sequence data, the Omicron variant now represents more than 98% of Covid-19 cases identified in France.

Easing behavior

In the current epidemic recovery, Arnaud Fontanet also questions the “easing of behavior that anticipated the lifting of measures, as has often happened in the past”. The announcement of the cessation of the mandatory masks was announced a few weeks ago and was accompanied by a decrease in the number of positive cases, which may have encouraged a relaxation of compliance with barrier measures.

However, it is partly at this point that the future spread of Covid-19 is playing out, according to Institut Pasteur forecasts.

Projections from the Institut Pasteur regarding the increase in transmission rates of Covid-19 with an easing of barrier gestures from March 7 (B) and March 14 (A)
Projections from the Institut Pasteur regarding the increase in transmission rates of Covid-19 with an easing of barrier gestures from March 7 (B) and March 14 (A) © Institut Pasteur

“In all the scenarios studied, the peak of cases remains much lower than the peak in January,” the researchers explain, but “it could exceed 100,000 daily cases by March in scenarios where transmission rates increase very significantly after release. ” .

Back to school was able to play

“There was also the start of the school year,” adds epidemiologist Arnaud Fontanet, “we have clearly seen that the regions where the incidence is starting to rise again are the regions that came back from vacation on February 21 with very high incidences. 9- birthdays.

“The Covid-19 positivity rate appears to be rising again in Zone B, ten days after the start of the school year,” noted Guillaume Rozier, creator of the CovidTracker platform, last Monday.

The impact of the spread of Covid-19 on schools has been discussed several times since the start of the pandemic. It is complex to manage because it means protecting children and their families from infection while ensuring good educational continuity.

Since Monday, the mask is no longer mandatory in schools in France, but it remains recommended for positive people and contact cases at risk, symptomatic people and health professionals.

March favorable for Covid-19?

The link between the weather and the spread of Covid-19 has been pointed out several times since the start of the pandemic. In the same way as other respiratory viruses, SARS-CoV-2 seems to circulate better in colder weather, because in winter the population tends to stay in closed places and ventilate less, facilitating infections. In addition, the immune system is more vulnerable and therefore they defend themselves less well when it is cold.

And the month of March seems to have been favorable for Covid-19 thus far. It’s “a month where we know that this virus is circulating,” Arnaud Fontanet recalled. In 2020, it was during this period that the first wave spread in France. “Think of March 2020, this is the month we had to lock up,” notes the epidemiologist. The third incarceration in April 2021 also took place after a peak in contamination in March.

“After that it should get better and we can hope that with spring we will also enter a period” when the circulation of the virus will be less important, he adds.

· Towards a major revival?

In its most pessimistic scenarios, the Institut Pasteur estimates that the peak of contamination “could exceed 100,000 daily cases in March”, a high figure but “much lower than the January peak”.

As always, these projections remain subject to various uncertainties. We do not know the duration of protection of vaccines, nor that of people infected with Omicron in recent weeks. On the other hand, new variants can be a game-changer.

“We cannot believe that in 2022 there will be no new variants of concern, in 2021 there were five,” recalls Yves Coppieters, so “there will undoubtedly be other variants”.

Salome Vincenton

Salome Vincenton BFMTV journalist