The current circulation of the Coronavirus Sars-CoV-2 is “characterized by Omicron sub-lineages and wide genetic diversification. More than 230 descendants “, ‘sons’ of Omicronthe variant that was the undisputed protagonist of the 2022 pandemic, “e more than 30 recombinantsi “. These variants” are monitored and evaluated by the World Health Organization on the basis of criteria of genetic constellations of mutations, of increased prevalence in a geographical area, as well as any evidence of phenotypic changes “. on the evolution of the virus is the WHO in its weekly report on Covid.
The high number of lineages also confirms what was also observed by Marco Cavaleri, head of the strategy for health threats and vaccines of the European drug agency Ema, who in recent days had highlighted how Sars-CoV-2 was “still rather unpredictable. “. A relevant fact, Cavaleri had pointed out, is that “it is changing at a crazy speed and continues to do so”. The WHO in its focus on variants explains that all of these lineages produced under the Omicron family “have several additional mutations, but most of them are not worthy of concern, even on the basis of current knowledge of relevant genetic sites”.
Here is the overview traced by the WHO: “Globally, from 19 August to 19 September 2022, over 120 thousand viral sequences were shared through the Gisaid database. Among these, almost 119,500 were Omicron, which accounts for 99% of all viral sequences reported globally in the last 30 days. At Omicron, starting from epidemiological week 35 (29 August-4 September 2022), the descendant lineages grouped under BA.5 show the highest relative prevalence (76.6%) , followed by the BA.4 group (7.5%). In the same period, the other ‘sisters’ – i.e. the BA.3 group, the BA.2 group (excluding the Centaurus BA.2.75) and the BA .1 decreased in global prevalence to less than 1% WHO explains that to date “6 strains are currently classified as Omicron sub-variants under monitoring”.
Chapter BA.2.75, that is the sub-variant of Omicron 2 baptized on the social Centaurus, is dealt with separately. And WHO explains that “BA.2.75 is monitored for 9 additional mutations observed in the peak compared to its ‘parent’ BA.2 lineage”; 4 are within the receptor binding domain (Rbd) and at least one of these Rbd mutations “has been associated with immune leak” in the previous variants. “The global prevalence of BA.2.75 – specifies the WHO – is low (1.26% at week 35), but has increased in recent weeks”.
Meanwhile, a total of 48 countries have reported the detection of Centaurus; most of the sequences reported come from India. And Centaurus has already ‘calved’ too: one of its descendants, BA.2.75.2, shows 3 further mutations on Spike. The other emerging sub-variants under monitoring are evolutions of BA.5.1 (with the addition of other mutations), BA.5.2, BA.5.2.1 and so on. These are sub-lineages with mutations in the Rbd positions with phenotypic effects (such as antibody leakage, changes in binding affinity with the ACE2 receptor, and so on). Also in this case the WHO specifies: “The prevalence of these Omicron sub-variants under monitoring is still low, but increasing in the last 4 weeks.