Les autorités sanitaires françaises ont peaufiné leurs procédures de suivi de la progression des variantes du coronavirus de manière "plus précise" et "plus réactive". </p><div> <p>"Aujourd'hui, il existe une variété croissante de variantes, ce qui signifie que rechercher spécifiquement une, deux ou trois variantes ne répond plus au besoin de surveillance du problème des variantes" SARS-CoV-2 "", a expliqué en conférence de presse Sibylle Bernard- Stoecklin, de la Direction des maladies infectieuses de Santé publique France.
As of this week, health authorities will stop releasing information about the distribution of “variants” and instead move to “mutations” (the process by which the strain of coronavirus changes to adopt new variants) in order to more accurately track them. disturbing variations.
All positive tests will continue to be screened, to detect “worrisome variants” of the coronavirus. But new screening kits will focus on tracking specific mutations found in a significant number of variants.
Since the end of May, laboratories have started to equip themselves with new kits, which will become the only ones authorized from mid-June.
Three mutations of interest
This method was introduced in January to identify the emergence of the Alpha variant, first identified in the UK in December 2020, and now the majority of positive cases in France.
Three mutations were retained: E484K, E484Q and L452R. Present in particular in the Beta variant (identified for the first time in South Africa) and the Gamma variant (Brazil), before the arrival of the Delta variant (subline from India).
They are considered “of interest” because they may be able to evade the immune response or have a higher transmissibility or severity of infection.
The list is limited to three because “the more mutations you add to a screening kit, the more the sensitivity decreases,” said Bernard-Stoecklin.
Since the end of May, laboratories have started to equip themselves with new screening kits, which will become the only ones authorized from mid-June.
While this strategy allows results to be obtained more quickly than sequencing, which consists of analyzing the entire RNA (ribonucleic acid) of the virus, it has many limitations.
First, French analysis laboratories are equipped with different kits, which do not all detect the same mutations.
Second, a positive result means that there is a “suspicion” of the presence of a worrying variant, but this can only be confirmed by sequencing.
Finally, since the same mutation can be present in several variants, the same screening result could be attributed to different variants according to the laboratories.
For example, the variant responsible for a cluster in Bordeaux at the end of May (similar to the Alpha variant but with several additional mutations), could be wrongly classified as a Beta or Gamma variant – or as an indeterminate variant or without a variant at all.
In recent weeks, Public Health France had warned that the distribution percentages of the various worrying variants were “to be interpreted with caution”.