The original SARS-CoV-2 virus, at the origin of the Covid-19 pandemic at the beginning of 2020, has long since disappeared in France, giving way to several successive variants, until the highly contagious Omicron becomes widespread in late December 2020. December 2021. With its various sub-variants, it has contributed greatly to three waves of infections.
The appearance of this variant, which presents many mutations compared to the historical strain of the virus, was not a surprise: the detection by British laboratories of the Alpha variant in late 2020, the scientific community knows that SARS-CoV- 2 can change.
Strong BA.5 sublineage progression
It is possible to observe the circulation of a variant in French territory thanks to sequencing: carried out from RT-PCR samples from patients with Covid-19, this molecular biology technique makes it possible to read the complete genome of SARS-CoV-2 and detect new mutations. The data can then be shared in the international Gisaid database (for global initiative to share data on avian influenza“global initiative to share data related to avian influenza”) or in the European surveillance system TESSy of the European Center for Disease Prevention and Control (ECDC).
The evolution of the estimated share for each variant is still subject to several biases (delay in publication, late development of sequencing and evolution of the national strategy, etc.), but these data, updated every week, show the progression of the variant Omicron in metropolitan France. .
The following table lists the characteristics of the main variants, according to the WHO classification, which baptizes each of them with a letter of the Greek alphabet, a denomination considered less “stigmatize” than its geographical origin. The best “worrying” (or VoC for concern variant) are listed for their transmissibility, their virulence, or even the lower efficacy of vaccines against them. Variants can be added to follow (VoI, for interest variant). Sometimes the OMS degrades certain variants when their circulation decreases.
The screening technique, complementary to sequencing, makes it possible to directly monitor mutations and their evolution between infections, instead of reading the entire genome of the virus. This method does not allow variants to be identified, but has the advantage of being able to be used on a larger scale. As of early August 2022, around a quarter of positive tests for SARS-CoV-2 benefit from screening each week, according to data from SI-Dep, an archive that lists antigen and PCR tests.
The latest results show the progression of the L452R (or L452Q) mutation. Previously, this mutation was mainly carried by Delta and used to identify her. It allows to follow the evolution of certain sub-variants of Omicron that circulate, such as BA.4, BA.5 or BA.2.12.1.
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