Covid-19: figures and maps to understand the sixth wave

SCIENCE – You have to go back to February 8 to have a worse daily record. The Directorate-General for Health (DGS) has identified 217,480 positive cases of Covid-19. The updated figures for Wednesday, March 30 are those published the previous evening, that is, Tuesday, March 29.

The sixth wave of coronavirus, therefore, continues its course, driven by the relaxation of barrier gestures, the lifting of restrictions and the dominance of the subvariant Omicron, BA.2. With some delay, hospital admissions continue to progress as well as resuscitation for a few days.

While the Pasteur Institute models on which the government was based were expecting a peak in late March, is the situation alarming? If it could be, it still isn’t. One indicator in particular has little hope that it will be confirmed or invalidated in the coming days. The following graphs and maps provide a better understanding of the situation.

An increase in cases that seems to be “slowing down”

First of all, remember that if more than 217,000 cases were reported on March 29, the figures for Tuesday are still very high compared to the rest of the week (because many tests are done and validated on Monday, then of the weekend). ).

In the chart below, we see that if we soften the number of cases for a week, we are on average 133,485 cases. However, the blue curve continues to rise.

But a weak signal, which will obviously require confirmation, is striking. The growth rate of the epidemic is declining. If we look at the percentage change between this Tuesday and the previous one, we see that it is 20%, while it has exceeded 50% a week before.

Overall, this growth rate has been declining over the last four days, as shown in the following graph. Possible good news to take with a grain of salt.

A weak signal that needs to be strengthened

In fact, the cases identified by the DGS are sensitive to various variations in the notification of cases. Thus, on Tuesday, March 15, the pollution seemed to increase less rapidly, but the next day it seemed that they had exploded.

To ensure that there is a real change in trend, we need to look back at the data, in particular from those published by Santé Publique France, which show the number of cases on the date of the screening, with three days of delay. .

The following graph summarizes the status of the various Covid-19 monitoring indicators. We see that the incidence curve is in full swing.

If we look below the growth rate for a week of the incidence according to the screening date, we see that it is still high, around 40%.

If there is no problem with the DGS rises, we should see the start of a slowdown in the next few days, especially on Thursday evening. It is on this date that the number of people who tested positive will be revealed on Monday 28 March.

If this lower growth is confirmed, it will have to continue in the next few days, until it becomes negative. If this decline is also confirmed for a few days, then we can say that the peak of the sixth wave is possibly behind.

It will be interesting to check the evolution of the situation at a more local level. For the time being, the map of France’s incidence rate shows an increase in all metropolitan departments, with the exception of Lot-et-Garonne (-1.4%).

An unrestricted peak?

If there is a peak in a few days, the scenarios calculated by the Institut Pasteur will have been, therefore, rather correct. And this peak is not due to restrictive measures, but probably to the fact that vaccination and acquired immunity after the January wave will prevent the circulation of the virus.

In the latest simulations available from the Institut Pasteur on March 22, the peak was forecast for the end of March, depending on the increase in our contacts at risk (and therefore the circulation of the virus).

Given the current situation (advanced vaccination and a lot of natural immunity acquired through the fifth wave), it is likely that if the wave of cases does not increase, hospitalizations, resuscitation and deaths should also be limited.

These elements make it possible, above all, to understand why the government is committed to ensuring that the lifting of restrictions does not lead to overcrowding in hospitals. However, this level of pollution will be a major burden, both for the hospital and for death.

The Scientific Council, in a March 11 opinion, recalled that “approximately 18,000 Covid-related deaths have occurred in France since December 15, 2021 (a significant portion of which is linked to Omicron variants, the so-called mild variants), and this, with a certain form of trivialization and indifference ”.

Finally, it should be remembered that the Pasteur Institute models are not predictions. Therefore, they can be wrong if the assumptions made are not verified. The least certain hypothesis, Simon Cauchemez, a modeler at the Institut Pasteur, reminded us on March 22, is the duration of immunity after Omicron infection. The model assumes that it is not possible to take Covid again before April 1 if someone has been infected with Omicron.

Otherwise, the peak could be much larger and come later. On the other hand, the model does not take into account the climate that will be softer. The Pasteur Institute is working on a new, more accurate model.

See also a The HuffPost: Deltacron variant, multiple mutations … when to worry?

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