Covid-19 : pourquoi les variants BA.4 et BA.5 ont été classés comme "inquiétants" par les autorités européennes

Covid-19 : pourquoi les variants BA.4 et BA.5 ont été classés comme “inquiétants” par les autorités européennes

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The European Center for Disease Prevention and Control has placed the two sub-variants BA.4 and BA.5 of Covid-19 in the category of “variants of concern”. Both could be responsible for a new wave of contamination in Europe in the coming weeks, according to European health authorities.

The BA.4 and BA.5 variants will undoubtedly have to be watched closely in the coming weeks. In a press release published last Saturday, May 14, the European Center for Disease Prevention and Control (ECDC) called on European states not to lower their guard against the spread of these two sub-variants, belonging to the Omicron line.

Circulation of these two strains of SARS-CoV-2 “is currently low,” the statement said. But according to the ECDC, BA.4 and BA.5 “will become dominant in the coming months”. This could gradually lead to “a significant increase in the number of cases” of Covid-19 contamination.

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MAINTENANCE. Covid-19: Omicron BA.4 and BA.5 variants “could arrive in Europe before mid-June”, according to Professor Flahault

If for the time being, nothing allows us to affirm that these two sub-variants would be more virulent than the BA.1 and BA.2 strains, the ECDC has decided to classify BA.4 and BA.5 in the category known as “worrying variants”. Both were previously part of the “interest” variants.

They were identified in South Africa at the end of 2021, where they are now the majority. In France, BA.2 remains the majority in the country (it represents 99% of contaminations in the country), but BA.4 and BA.5 have already been detected in France.

According to data communicated by Santé Publique France on May 2, two cases of contamination with the BA.4 variant and six cases of infection with BA.5 have been recorded in the country: the two sub-variants are closely monitored by the authorities. sanitary.

What do we know about these two variants?

According to the ECDC, these two strains “appear to be more transmissible than the previous” subvariants of Omicron. The ECDC is concerned about their genetic profile, which is based on mutations of interest closely monitored by the authorities. Two of them have been isolated by scientists:

  • The L452R mutation : this mutation had already been detected in the Delta variant. It “is associated with a greater affinity of the virus with the ACE2 receptor which allows the virus to infect human cells, specifies Professor Antoine Flahault. We can therefore be dealing with a more transmissible variant than Omicron and escaping the acquired and vaccine immunity, but not necessarily to a strain associated with greater severity.”
  • The F486 mutation : this “is associated with a reduction in the neutralization of antibodies and could therefore indeed play an important role in vaccine escape”.

Read also :
Covid-19: transmissibility, resistance to vaccines… In BA.4 and BA.5, mutations that raise questions

According to the European Center for Disease Prevention and Control, BA.4 and BA.5 may have the ability “to evade immune protection induced by previous infection and/or vaccination, particularly if this has waned with time”.

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