what we know about the BA.4 and BA.5 variants, new Omicron strains

Two new Omicron sub-variants detected in South Africa in January have been detected in France. What do we know about these variants classified in the category of “variants of interest” by various world organizations?

While the Covid-19 epidemic has been declining for a few weeks in France, two new variants are causing trouble: BA.4 and BA.5. These are two new sub-lineages of the Omicron variant which are already carrying a new wave of contamination in South Africa. They currently represent 70% of the sequenced strains, hence the fear of a new wave of contamination similar to the one currently raging in the country which has a positivity rate of nearly 17%.

Detected in South Africa, just like the Omicron variant last November, BA.4 and BA.5 are classified as “variants of interest” by the World Health Organization (WHO) and “are the subject of ‘reinforced surveillance on the basis of their genetic profile’ from Public Health France (SPF).

Jacob Lemieux, an infectious disease specialist at Massachusetts General Hospital, said a few days ago that these subvariants appeared to be “causing an exponential increase in positivity rates” given the “alarming” situation in South Africa, reports The Harvard Gazette.

Already present in more than twenty countries

On April 26, one case of BA.4 and two cases of BA.5 were detected in France, the health authorities indicated during the weekly epidemiological update on April 28. They have also been detected in more than twenty countries such as Botswana, Australia, China, England and Denmark. These subvariants, which have identical spike proteins, are both very similar to the Omicron BA.2 subvariant but contain several mutations, one of which is of particular concern.

This is the L452R mutation which is “described as one of the factors associated with the significant transmissibility of Delta”, this highly contagious variant which represented 100% of cases in France last October. Asked by La Dépêche, Antoine Flahault indicates that this mutation is “associated with a greater affinity of the virus with the ACE2 receptor which allows the virus to infect human cells”, which gives rise to more transmissible variants.

A less effective vaccine?

Another questionable mutation: F486. The latter has already been observed in mink farms and is involved in an immune escape phenomenon, which could reduce the effectiveness of vaccination against Covid-19. These two subvariants would also be resistant to the protection conferred by infection with the BA.1 variant, even more so in non-vaccinated people, according to another study not yet peer-reviewed.

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For the time being, a new wave is not on the agenda in France and in Europe because “no worrying epidemiological or clinical element is associated with them”, specify the French health authorities. “There is no cause for alarm with the emergence of new sub-variants. We are not yet seeing a major spike in cases, hospitalizations or deaths,” said Dr. Matshidiso. Moeti, WHO Regional Director for Africa. Be careful all the same because in the past, several epidemic waves have hit Europe a few weeks after South Africa.

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