Alpha, Beta, Delta, Lambda, Mu… Since the appearance of Covid-19 in November 2019, the initial strain of the virus has undergone numerous mutations. If these developments move it far enough away from what it was at the start, the new organism is qualified as « variant ». At present, in France and throughout the world, it is the Omicron BA.2 sub-variant which remains the majority, with 51% of the cases identified. June, however, saw a surge of two other sub-lineages, BA.4 and especially BA.5.
“The vast majority of viruses are characterized by constant genetic evolution, more or less rapid depending on the virus. It occurs in particular following mutations introduced into their genome. For a virus like Sras-CoV-2, the emergence of variants over time is therefore an expected phenomenon,” explains Public Health France.
Since May 31, 2021, the World Health Organization (WHO) has decided to give these variants names of Greek letters. On the one hand, this must serve to ensure that they are retained easily. On the other hand, this decision is intended not to stigmatize the countries where the first case of a variant has been identified. The Alpha, for example, had been referred to as the “English” variant when it first started circulating.
The Russian Roulette of Mutations
Most mutations go unnoticed. Some may even make the virus less dangerous. On the other hand, they can also make it more contagious, more virulent, or less vulnerable to the immune response of the sick host, as recalled by the European Center for Disease Prevention and Control (ECDC).
According to the characteristics acquired with the mutations, the WHO classifies the variants into three categories: variants of concern (VOC) are of greatest concern, while variants of interest (VOI) is the object of an attentive surveillance. Les VUM (virus under monitoring) are under evaluation. The VOCs currently in circulation, according to the ECDC, are Omicron and its subvariants BA.2, BA.4 and BA.5.
The Omicron variant had been classified VOC on November 26, 2021. Although it remains less virulent than the Delta, it is on the other hand much more contagious. It had supplanted the Delta in France and internationally from January 2022. According to South African and Scottish data, it is 70% more contagious than its predecessor, and carries a risk of reinfection five times higher. raised.
The possibility of a future more pathogenic variant
On the other hand, the risk of hospitalization is 70 to 80% lower. Indeed, the specialists report that the pneumopathies remain less severe than with the previous variants.
The progression of these BA.4 and BA.5 sub-lineages was meteoric in June. Today, in France, 41% of positive tests are linked to the second.
While Omicron and its subvariants appear to be of low risk to most affected individuals, there is always the possibility that Covid-19 may mutate in a more worrisome direction. “The hypothesis of a future dominant variant that is more pathogenic than Omicron, either intrinsically or through greater immune response evasion, cannot be ruled out,” thus considers Public Health France.