"Only" 3.1 million new cases of Covid-19 recorded worldwide.

The World Health Organization (WHO) announced Thursday, February 11, that the number of new infections with Sars-CoV-2 fell by 17% compared to the previous week.

It is even the fourth week in a row that it is in decline.

That is 40% of new positive cases per day less than in early January, according to Le Parisien.

However, between the appearance of new more contagious variants, the setbacks of vaccination campaigns in Europe, the heated debates on the need or not to establish a new "hard" containment to stop the spread of Sars-CoV-2, the the current climate rather gives the impression of an epidemic more virulent than ever.

"Not bad news"

So there would be, as with the cold, a difference between the epidemic "felt" and the real dynamics of the pandemic?

This is, in any case, what the WHO suggests, which even specifies that this downward trend is observed on all continents.

However, it is not uniform since it is sharper in countries like India, Japan or Spain and much lighter in France or Germany.

"This is certainly not bad news, but it is still necessary to know how good it is," notes Jonathan Stoye, virologist and head of research at the Francis Crick Institute in London, contacted by France 24.

The overall drop in new cases comes mainly from "large countries" which concentrate the lion's share of declared contaminations.

This is the case for the United States (-20%), the United Kingdom (-25%) or even Brazil (-10%).

These declines, significant in volume, can "give a deceptive impression of a general decline", specifies Jonathan Stoye.

The WHO data does indeed reflect only very imperfectly "the situation in other countries which do not have the means to organize large screening campaigns and therefore only bring up incomplete data", continues this expert.

If the decline in new cases worldwide noted by the WHO is therefore to be taken with a grain of salt, the fact remains that it seems real in these "large countries".

"The effect of the more restrictive health measures taken at the end of the year is now being felt, which gives the impression that we are starting to know how to control the spread of this virus in terms of the health response", analyzes Jean- Marie Milleliri, epidemiologist, contacted by France 24.

This is particularly evident in the United States.

The fall in new contaminations since January "seems to be the direct result of the stricter health measures taken by the new American President Joe Biden in recent months", underlines Daniel Dunia, virologist at the Toulouse physiopathology center of Inserm, contacted by France 24.

The beneficial effect of health measures is also "evident in Spain and the United Kingdom, where there has been the establishment of reinforced containment," said Jonathan Stoye.

And the variants in all of this?

But there is also another factor to consider in the equation: the individual immunity of people who have already been infected with Sars-CoV-2.

The spread of the virus is receding "not only because of social distancing and containment measures, but also because once outside, it has fewer individuals it can infect because some of them are already immune because they have already had it ", explains Jean-Stéphane Dhersin, deputy scientific director of the National Institute of Mathematical Sciences and specialist in the modeling of epidemics, contacted by France 24.

But this specialist specifies that these WHO data only tell part of the story.

They essentially show the trajectory of "historical" Sars-CoV-2 ... without reflecting the emergence of variants.

"What is reflected in the figures is the evolution of cases of contamination with the majority strain of the virus, which is still the original form of Covid-19", he summarizes.

For him, the world could be, in reality, at a tipping point: the historical variant is coming to the end of the race because the authorities have succeeded in controlling it, which the WHO figures show, but the new forms of Sars -CoV-2 are ready to take over.

To have a more realistic vision of the evolution of the epidemic, "it would be necessary to carry out massive sequencing of the virus in the infected population to know as quickly as possible when a new 'mutant' appears and if it is more contagious or dangerous" , assures Jean-Stéphane Dhersin.

Without that, we risk continuing to blindly trust figures from the WHO which cannot take into account these variants which, little by little, are becoming smaller.

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