Since the beginning of 2020, several Covid epidemic waves have followed one another, of varying magnitude. The one currently raging in France is the 7th wave. 3 scenarios are possible for autumn 2022. Curves in graph and key dates of the epidemic peaks of the Covid waves.
[Mis à jour le 21 juillet 2022 à 12h46] The Covid-19 epidemic has evolved in waves. To date, 7 waves are recorded between March 2020 summer 2022, marked by the influx of patients in hospital and intensive care. after a slight plateau in early March 2022. Curve of the first wave, the second, the third, the fourth and the fifth, the sixth, the seventh, peak, hospitalizations… Here is the evolution of the Covid epidemic in France with its key dates.
What are the scenarios for fall 2022?
Just before its dissolution, the Scientific Council issued its hypotheses concerning the evolution of the pandemic in France.
- Scenario 1: A succession of epidemic waves linked to the emergence of sub-variants of Omicron, with a lower hospital impact compared to that of the waves linked to VOCs at the start of the pandemic. This is the scenario we are currently seeing with wave BA.4/BA.5. The current subvariant of concern is the BA.2.75 appeared in Indiawith a transmissibility advantage over the BA.2 variant already present in this country.
- Scenario 2: A seasonal resumption of circulation of an existing variant or of a variant antigenically close to an existing variant. This epidemic resumption in the fall or winter is expected due to the decline in population immunity over time and the greater transmissibility of coronaviruses in the cold season. It is not possible to predict whether one or more variants will circulate, and which variants will be affected by this epidemic resumption, co-circulation depending on the relative contagiousness of the variants, and the cross-immune protection existing between the variants. We can hope that the hospital impact associated with this resumption of an already known variant will be manageable due to the cross-immunity existing between the variants that have circulated up to now, even if this cross-immunity is imperfect.
- Scenario 3: The emergence of an X variant endowed with an immune escape capacity and sufficient contagiousness to be responsible for a new epidemic wave. This “successful” emergence could occur at any time, anywhere in the world, with a higher probability in places where the emergence mechanisms are most active: significant multiplication of the virus, zoonotic reservoir, immunocompromised population of large cut. The severity of the clinical manifestations associated with this new variant is unpredictable, and can range from lesser to greater severity. This scenario has a relatively high level of probability.
7th wave of Covid: right now
The lull was short-lived. After a weakening in the number of Covid cases, all indicators show a resurgence of the virus since the end of May, particularly in Ile-de-France. This epidemic wave is notably carried by two other sub-variants of Omicron which are in the process of imposing themselves in France: BA.4 and BA.5. “Probably due to their ability to escape immunity acquired through infection and/or vaccination, especially if this has waned over time“, reports the European Center for Disease Control (ECDC) in a report of May 13. In mid-June, the average number of confirmed cases is around 40,000 per day. For the moment, the peak of the 7th wave does not appear to have been achieved.
6th wave of Covid: end of March – mid April 2022
Some epidemiologists have suggested a 6th wave, at the end of March 2022, with an incidence rate and a total number of positive cases which were going up. Nevertheless, this wave was smaller scale than previous waves (see curve below). According to figures from Public Health France, the number of cases gradually decreased around April 5 until reaching a plateau of around 20,000 new cases per day around May 20, 2022. the rise. The peak of the 6th wave was around the March 31, 2022.
5th wave of Covid: November 2021 – February 2022
The fifth wave of the COVID-19 epidemic started in early November 2021. The incidence rate has increased sharply and exceeded the level reached in previous waves. Despite the increase in incidence observed in all age groups at the start of this 5th wave, the virus seems to have mainly circulated among the youngest. This wave first conveyed by the variant Deltawas then marked by the emergence of a new variant called Omicron. In this worrying context, the government has relied on a recall campaign. The incidence rate peaked around January 24, 2022 (with 3,800 positive cases per 100,000 population). The peak of hospitalizations was reached on February 7, 2022 with more than 33,000 people hospitalized. The curves then slowed down around mid-February. In March, we can say that France came out of the 5th wave.
4th wave of Covid: July-August 2021
On July 21, 2021, Prime Minister Jean Castex confirmed on TF1 that France had entered its fourth epidemic wave. At that date, the curve of hospitalizations was still low because we know that it takes on average 2 to 3 weeks for the increase in cases to affect the number of people hospitalized. The peak was reached in mid-August. The generalization of sanitary pass pushed the French to go to get vaccinated which made it possible to bring down the curve of hospitalizations. The peak of the 4th wave was reached at the mid-August 2021 (around August 12, 2021)
3rd wave of Covid: March-April 2021
After experiencing a decline from November 16, 2020, the epidemic is started to rise again in mid-March 2021, with an average of new cases per day of 50,000. “Yes the third wave is here and it is hitting us hard” alerted the Prime Minister, Jean Castex, before the National Assembly on April 1, 2021. Monday March 29, 2021, the number of people in intensive care exceeded that of the peak of the second wave in the fall. This is the highest number since April 22, 2020. The health situation is particularly critical in Ile-de-France where hospitals are saturated. The highest number of critical care admissions was reached on April 12, 2021 with 495 new admissions. The peak of the 3rd wave was reached on April 12, 2021 for hospitalizations and April 13 2021 for resuscitation.
2nd wave of Covid: September – November 2020
The Scientific Council alerted at the beginning of September 2020 to the occurrence at the end of that same month ofa second epidemic wave. “Circulation of the virus resumed during the summer of 2020 throughout France, particularly among young adults. The number of cases diagnosed each day reached 10,000 on September 1.“, he explained in a note of October 26. A drop in the figures was observed during the second half of September (on average 15,000 new infections per day). As of October 1, 2020, “there is an extremely rapid rise in the number of new caseswhich follows a general drop in temperatures (drop reaching 25°C for the maximum in places) which began between September 20 and 25 depending on the region“, continued the Scientific Council. The epidemic then progressed in France to reach in mid-November [autour du 15 novembre] a number of people hospitalized slightly higher than the peak in mid-April (about 32,000 people hospitalized each day between November 11 and 20). In mid-November, the epidemic is in decline. On December 14, 2020, the daily number of new cases hovers around 4,000. The peak of the 2nd wave was reached between 12 and 19 November 2020.
1st wave of Covid: March – May 2020
Since the first official cases recorded in France on January 24, 2020 by Public Health France, the numbers of new cases and new deaths from Covid-19 have increased dramatically. increasing until the end of March. In other words, from the end of January to the end of March, France was in ascending phase. From April 3, 2020, the impact of the epidemic was major and “France was in a high plateau phase“indicated Jérôme Salomon, director general of health on April 10. The number of people hospitalized was the highest on April 14 (over 32,000) to drop gradually between April 20 and early June (around 15,000). Between June 15 and September 20, 2020, the number of hospitalized patients stabilized around 5,000 and the number of people in intensive care around 400: France was then in a low plateau phase. The numbers began to rise again in late August, leaving predict the start of a second wave. the first wave peak took place, according to the curves, between April 6 and 10, 2020.
Bell curve: characteristic of viral diseases?
For each of the waves, the epidemic curve appears to follow the bell curve (see curves above). The bell shape (also called curve of Gauss in mathematics) is typical of curves of evolution of an epidemic called “by propagation”, as is the case with most human-to-human diseases (viral diseases). If we analyze the epidemic curve of a viral disease, we always notice an ascending phase at the start of the epidemic, then a bell shape which corresponds at the peak of the epidemic, a stagnation in the number of new cases and finally, a downward phase, where the number of cases gradually decreases. For some scientists, this typical “bell” shape represents an indicator that would announce that the peak of the epidemic has been reached and that the disease is in a very decreasing phase.
Sources: Covid-19 epidemiological update, Public Health France // Geodès curves – Public Health France (hospital data) // Note from the Covid-19 Scientific Council: a second wave resulting in a critical health situation – October 26, 2020