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Covid-19: which variants are circulating in France and which are monitored elsewhere? -Coronavirus

  • 1 BA.4 and BA.5 still ultra-dominant in France and around the world

  • In the competition between variants, Omicron has crushed the competition since its appearance in late 2021 and has expanded across the world. Over the millions of contaminations it generated, it acquired mutations and gave birth to sub-lineages like BA.2, then BA.4 and BA.5. It is the latter two that circulate massively today on all continents.

    BA.5 is the most detected on a global scale with 83% of the sequences deposited on the GISAID genomic monitoring platform, between August 6 and September 5, recalls Public Health France (SPF). BA.4 only represented 7%.

    France has experienced a new epidemic outbreak of covid-19 since the start of the school year. The variant responsible is undoubtedly BA.5, which was detected in 93% of people infected in the Flash sequencing survey of August 22, the last of which we know the results.

    “After having generated a first summer wave in June, we are witnessing a pure and simple return of BA.5 for this autumn, as was the case with Delta last year”, recalls Mircea Sofonea, master of conferences in epidemiology and evolution of infectious diseases, at the University of Montpellier.

    Within the BA.5 family itself, there are also descendants, with an increase in the presence of BA.5.2 and BA.5.2.1 in the country.

    (Public Health France)
  • 2 BA.2.75 thrives in India

  • During its first detections in June, the BA.2.75 sub-lineage appeared to be one of the most serious candidates to replace BA.4 and BA.5 in the world. Since then, he has been closely followed by the international community. Arbitrarily nicknamed “Centaur” by several media, it has developed strongly in India where it became the majority at the beginning of August. Rather reassuring, Public Health France observes that “the epidemiological situation in India seems to be improving, with a decrease in incidence and a number of deaths which remains low”. BA.2.75 is experiencing increasing circulation in other Asian countries, such as Japan and Singapore, but in Europe it remains at very low levels. In France, it had only been detected in 0.3% of the positive tests studied by sequencing during the flash survey carried out on August 22.

    Why such a difference in presence between the regions of the world? “The growth of BA.2.75 in other countries is believed to be due to local effects and different histories because the further into this pandemic we go, the more countries’ immunological and epidemiological histories diverge. BA.5 is well established in France and, on the basis of the data we have today, there is very little chance that BA.2.75 will replace it,” says Mircea Sofonea.

  • 3 BA.4.6 particularly followed in the United States

  • The BA.4 sub-variant includes sub-lineages, one of which is particularly monitored in the United States, BA.4.6. It accounted for around 10% of infections there during the week of September 11 to 17, according to the Centers for Disease Control and Prevention (CDC). A proportion in constant progression since June but which does not explode. “He doesn’t seem to win against BA.5”, even notes SPF. Globally, it only represented 3% of the sequences deposited in the GISAID database and, in France, it was only detected in 2% of the tests studied during the flash survey in mid-August.

  • 4 How could new variants supplant current viruses?

  • To replace a variant, the new one must have a transmissibility advantage. “During the first year of covid-19, marked by measures such as confinements and curfews, the selection of variants was essentially done via their ability to be more contagious”, recalls Mircea Sofonea. With the progression of collective immunity acquired by contamination and vaccination, things have changed: “The second and third years of covid are dominated by a succession of variants which are essentially selected, apart from Delta, on their ability to escape the immune response,” continues the scientist. And to conclude: “Genomic surveillance is the sinews of war to identify who will be next responsible for future waves and what their properties will be in terms of immune escape, contagiousness and clinical factors (severity, escape from treatments such as antivirals and monoclonal antibodies).

    letelegramme Fr Trans

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