BA.2, the sister, advantaged? omicron



It is not a variant of coronavirus It's not something new, but BA.2 is in the focus of attention of virologists, epidemiologists and geneticists. This subvariant of omicronwhich emerged in November, shortly after BA.1 –the most widespread omicron sublineage in the world–, is already 45% in Denmarkwhere the curve of cases once again draws a vertical wall after several days of decline. Are we facing the advantaged sister of ómicron, due to greater transmissibility? Does it have the ability to reinfect those who have been infected with Omicron BA.1? For now there are more questions than answers.

The Health Security Agency United Kingdom (UKHSA) has classified BA.2 as a “variant of interest”, not of concern. Like the BA.1 subvariant, BA.2 has more than 50 mutations, but a dozen of them are not shared with its “sister”, especially those found in the spike protein “S” – the “spikes” ” that the coronavirus uses to enter cells – and in ORF1a. Some experts have pointed out that the genetic differences between these two “sister” lineages of omicron are greater than those between the original Wuhan strain and the alpha (British) strain, the first variant of concern detected. One of these differences in mutations causes BA.2 cannot be easily identified by a PCR before genome sequencing, since BA.2 lacks the omission in protein S (the 69-70 deletion) that the BA.1 lineage does have. That's why some call it "stealth omicron".

Regarding its clinical effects, data are lacking, but hospitalization figures for covid in Denmark have not increased.

The Scandinavian country reported 45% of cases of BA.2 in the second week of this month. It should be remembered that Denmark is the country that performs the most sequencing in the world together with the United Kingdom. Samples of BA.2 are also significant in India, where it is said to have originated, Sweden, Israel and Singapore, and have been reported in 40 countries in totalaccording to the UKHSA.

Experts do not believe there is reason for alarm. The American geneticist and researcher Eric Topol, one of the reference scientists in the pandemic, points out that there are still no functional or epidemiological data showing significant differences with the BA.1 subvariant, although "the spread of BA.2 supports the hypothesis of that it has greater transmissibility, something difficult to imagine beyond its sister BA.1”. Topol stresses that there is much to be found out and that "there is no cause for anguish at this point, we already have enough of that".

The scientist JP Weiland, who correctly calculated that ómicron is 5 or 6 times more transmissible than deltahas estimated that BA.2 has a competitive growth advantage over BA.1 of 90% in Denmark and 120% in the UK.

A hypothesis that could explain its great speed of propagation would be a greater ability to infect vaccinated people or reinfect those who were infected months ago. "It may be more resistant to immunity in the population, we don't know yet," Anders Fomsgaard of Denmark's Statens Serum Institut told Reuters. There could be a possibility that people infected with BA.1 might not be immune from getting BA.2 soon after.” If so, perhaps this sixth wave would end up looking more like a mountain range than Mount Everest.



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