Rather than looking for variants when a PCR test is positive, Public Health France recommends focusing on the most worrying mutations.
The health agency thus selected the E484K, E484Q and L452R mutations, associated with a possible increase in transmissibility of the virus or a possible immune escape, that is to say a higher contagiousness and a risk of resistance to vaccines.
The goal: to improve surveillance by identifying the possible appearance of new variants and mutations, and to prevent their spread over the territory.
The weather is nice, it's hot, and the anti-Covid vaccination campaign opens to adolescents this Tuesday.
But there is no question of releasing the pressure in the face of the coronavirus and its variants - always more contagious - which appear over the months.
To avoid holes in the racket, the French screening strategy is evolving.
Henceforth, it is no longer the variants that will be sought in the event of a positive PCR test, but "the three mutations E484K, E484Q and L452R", indicates Public Health France in its latest epidemiological bulletin.
What will it change?
"The greatest vigilance" in the face of the Delta variant
English, Indian, Brazilian, South African, or rather Alpha, Delta, Gamma and Beta: today, it is difficult to see clearly between the many variants. On the other hand, what is certain is that to date in France, the Alpha variant, which has emerged in the United Kingdom, is still in the majority: “the proportion of suspicions [of this] variant is still predominant. and represents 74.6%, according to the analysis of the screening results in week 22 ”, ie the week of May 31 to June 6, indicates Public Health France.
The Delta variant, which appeared in India, is responsible for a further rise in contamination in the United Kingdom. British health authorities say it is 60% more contagious than the Alpha variant. It is much less present in France, but Public Health France notes "a recent increase in [its] detection in sequenced samples". It thus represents “between 2 and 4% of positive cases” of Covid-19, or “50 to 150 new diagnoses” per day, the Minister of Health, Olivier Véran, said on Tuesday. In addition, "the appearance of clusters with autochthonous transmission of this variant indicates that such transmission has started in France, which should lead to the greatest vigilance", insists Public Health France.
Until now, positive PCR tests were then subjected to screening tests for the Alpha, Beta and Gamma variants.
But the proliferation of variants is pushing France to adapt its screening strategy.
Look for mutations of interest
From now on, “the screening is evolving towards the search for mutations of interest, explains the health agency. The E484K, E484Q and L452R mutations were selected because they are associated with a possible increase in transmissibility (L452R) or a possible immune escape (L452R, E484K and E484Q), hence the need to monitor them in particular ”. In short: these are mutations that can give rise to strains that are more contagious and more resistant to vaccines. "The improvement of this strategy is based on the use of new screening kits by the laboratories", specifies Public Health France. In practice, "it's just the reagent that changes, the machines are the same," describes Dr. Lionel Barrand, president of the Union of Young Medical Biologists.However, we need to do tests on these new reagents, which detect other mutations than those detected until now ”.
Otherwise, “this is not a new approach, since we were already looking for mutations.
Except that in the conclusions, we were interested in the "geographical" name of the variant, which did not make sense since we can have several different variants in the same country, analyzes Dr Barrand.
Thus, an Alpha variant was found with and without the E484K mutation ”.
Besides, “we couldn't find any more.
We had in particular a version 4 of the English variant which came back with an Indian mutation, says Dr François Blanchecotte, president of the Syndicate of biologists.
We realize that this virus adapts to the public it meets by mutating.
It is therefore logical to adapt the surveillance strategy by targeting the main mutations ”.
"Follow the evolution of the virus on the territory"
For the biologists responsible for these more in-depth tests, “what changes are the targets: we will focus on these three mutations, which are of medical importance today. And maybe in a few months, we'll be asked to look for new ones, ”explains Dr. Barrand.
With this change, "it is a question of following the evolution of the mutations of the virus on the French territory", continues the biologist, thanks to this new more efficient strategy of sequencing-screening. These two complementary techniques work like two nets whose meshes do not have the same size. “With screening, we only find what we are looking for: the variants currently in circulation. Sequencing allows him to identify the mutations that are circulating, but also to find new ones. And if we find new mutations, their sequencing could allow us to identify a new variant of importance ”. "This detection results in a coding of the mutation with 3 digits and 2 letters, as is the case of the E484K mutation", adds Dr François Blanchecotte.
"Screening is good, but you have to know what to do"
And then, what can be the concrete effects of a more detailed screening strategy? A fundamental tool in epidemiological surveillance, the screening and sequencing diptych can strengthen the strategy to control the spread of the virus. “Provided that the management is changed, says Dr. Barrand. When there is a mutation that we absolutely want to avoid spreading, because there is a serious danger of contagiousness and increased vaccine escape, it is necessary, for people who test positive for this mutation, to organize a differentiated management with a more drastic isolation strategy, prescribed Dr Barrand. Because screening is good, but you have to know what to do. However, for the moment, there is no really framed strategy on this issue ”.
But already, "if we uncover a cluster that is developing significantly, we will look around the identified patient for all those who will present this characteristic mutation," reassures Dr. Blanchecotte.
A tracing which, despite the improvement in the health situation in France, remains decisive, especially on the eve of the summer holidays.
"We reach a level of vaccination, at a time when the French who remain to be vaccinated are perhaps more difficult to convince, recalls the medical biologist.
By identifying new appearances of mutations, we can act by concentrating vaccination on populations close to clusters, like what was done in Bordeaux, to increase their protection in the event of a mutation that is more contagious or resistant to vaccination. ".
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