what do the curves of the epidemic show one week after the end of the restrictions?

While measures to combat Covid-19 have been reduced since Monday, March 14, the number of contaminations continues to increase for all age groups and in all regions, while the number of admissions does not decrease. In its latest epidemiological point, Public Health France recommends maintaining barrier movements, especially to protect the most fragile.

Also read: The government is “extremely vigilant”, says Olivier Véran

About pollution

After peaking on January 24 with 567,851 positive samples in one day (and a weekly average of 365,000 daily cases), pollution dropped rapidly. But the pace in this fall has slowed since the end of February, and the lowest point was reached on March 3 with a seven-day average of 51,700 daily cases. Since then, the number of pollutants has started to rise again, rising from 51,800 to 86,000 a day on average between March 3 and March 18.

This increase in cases is also illustrated in the schools: 3,184 classes were closed on Friday 18 March against 2,693 classes the previous week.

In other countries, such as England, we are also seeing a very rapid growth in the epidemic, two weeks before France. Faced with the increased pollution, Austria announced return of the mask (FFP2) indoors from Wednesday and tightening of the rules for isolation of positive cases.

“European countries see the first effects of the randomness of their policies in dealing with the pandemic”have recently tweeted epidemiologist Antoine Flahault.

This is what the Institut Pasteur predicted in its models, published on Thursday 10 March, indicating that the recovery of the epidemic will largely depend on the degree of easing of barrier movements and the multiplication of French social contacts. In its most pessimistic scenarios, where “transmission speeds increase dramatically”Institute Pasteur estimates that the peak of pollution “may exceed 100,000 daily cases in March”. This high number remains “much much lower than the peak in January”which at its peak had reached a rolling average of 365,000 daily cases.

Why such a difference? Because the high level of circulation of the virus in the winter of 2021-2022 caused, from November 19, 2021 to March 3, approximately 16.15 million Covid-19 infections, reducing the number of individuals without immune protection against the virus. From now on “80% of people” is vaccinated and “A significant portion of the population has already been affected by the infectionstressed Yazdan Yazdanpanah. This immunity probably protects us. At least in terms of admissions. »

Read the decryption: Article reserved for our subscribers The beginning of the sixth wave or the backwash of the fifth? Institut Pasteur predicts several scenarios

In the hospital

The number of new admissions has stabilized and this is not necessarily good news. “In two days the number of admissions has not decreased”noted on Monday the Minister of Health, Olivier Véran, in The Parisian. Between March 14 and 20, the number of hospital admissions above the 1,000 limit per day increased on average. As of March 20, 1,642 patients were in critical care for Covid-19.

“Admissions to hospitals have been increasing again for eight days, and the number of deaths is more or less stable in the intensive care unit. Which means it’s not falling anymore.concerned epidemiologist Catherine Hill in Expressen.

The level of hospitalization will certainly start to rise again by following the contaminations, as it has done since the start of the epidemic, but it should remain limited if the number of new cases does not explode. “Our model does not quantify the impact on the hospital to predict in March, but it is likely to remain absorbable”assessed Simon Cauchemez, researcher at the Institut Pasteur, in World, Thursday, March 10th.

If the public hospital can still absorb a new wave of hospitalizations due to Covid-19, fatigue will weigh on hospital staff after two years and five epidemic waves that have drained its resources and delayed many care activities for decades. month.

“My fear is not so much what happens in the coming weeks, but more in the next six months”, Rémi Salomon, chairman of the medical committee for the establishment of AP-HP, explained on Monday about RMC. Because according to him, “The hospital is paradoxically more fragile than before the pandemic. »

Without even counting the loss of opportunities for patients with serious illnesses, Covid-19 also results in a high human load. Between November 19, 2021, when the circulation of the virus intensified significantly, and on March 14, 2022, 21,939 people died of Covid-19, an average of nearly 190 a day. The fact that the less virulent Omicron variant replaced the Delta variant in January 2022 has reduced the number of deaths, but very slowly. The number of daily deaths (in a moving average) has just fallen below the threshold of one hundred on March 16, 2022. This had not happened since December 6, 2021.

On the effects and predominance of the BA.2 variant

According to Yazdan Yazdanpanah, the increase in the number of cases is linked to “reopening of schools” after the holiday, to a probable “the population is declining”, but also to the predominance of BA.2, one of the sub-variants of Omicron. According to the latest epidemiological update from Public Health France, the latter was detected in the whole of mainland France in early March, with 52% of cases detected.

BA.2 is 30% more contagious than BA.1, another formerly dominant Omicron subgenus, a Danish study shows. “The study shows that if a household is infected with BA.2, there is an overall 39% risk that another member of the household will be infected within the first week. This risk is 29% if the household is infected with BA.1 ”pointed out the Danish Infection Control Agency.

This shortening can make future waves of pollution more “sudden”

Another concern related to BA.2: its “serial interval”, ie the number of days between one infection and another in the contamination chain, seems shorter than in its cousin Omicron. According to preliminary data published by Public Health England in its report on 22 February, that would be 3.27 days compared to 3.72 days for Omicron. This abbreviation could do more “suddenly” future waves of pollution. As an illustration, the influenza virus is not very contagious (its average reproduction rate is 1.5), but its serial interval of 3.6 days makes epidemics quite “explosive” : they rise very fast, but fall just as fast.

Vaccine protection is not reduced by this new sub-variant, according to a study by the British Health Agency. With two doses of vaccine, the effect is 10% for BA.1 and 18% for BA.2. With three doses, the effect increases to 69% for BA.1 and 74% for BA.2, then drops to almost 50% two and a half months later for both. In contrast, people who have not received a vaccine dose will be more likely to be infected with this new variant compared to BA.1.

Another reassuring point: BA.2 would not cause more serious cases than Omicron, still according to the UK agency. Data adjusted by age, previous infections, gender or even ethnic origin, even suggest a lower risk of hospitalization and the development of a serious form of the disease. However, these are early estimates and may change as data accumulates.

also read Article reserved for our subscribers Covid-19: a fourth dose vaccine for over 80s and the most fragile

The World Health Organization (WHO) Technical Advisory Group on the development of the SARS-CoV-2 virus also reviewed clinical severity data collected from South Africa, the United Kingdom and Denmark. He concludes that no difference in severity was reported between BA.2 and BA.1. Although it is possible to become infected with BA.2 after receiving BA.1, a person previously infected with Omicron remains “very protected” mod BA.2.

Public Health France informed that work was underway to more accurately estimate the transmissibility, severity and immune response release of BA.2 compared to BA.1.

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