Mumbai : Omicron is a variant of the SARS-CoV-2 virus that was first discovered in Botswana on November 11 2021 and designated a variant of concern by the WHO on November 26. Since this time, it has been transmitted worldwide and replaced Delta to become the dominant variant.
Omicron has since continued to evolve to have multiple different lineages, or genetically related subvariants. This includes the original Omicron BA.1 (B.1.1.529) and also BA.2 and BA.3.
BA.2 is more infectious than BA.1 and has now taken over or outcompeted BA.1 to become the new dominant form of the SARS-CoV-2 virus worldwide, with the WHO officially announcing this to be the case on March 22 2022.
The differences we have seen with Omicron relative to previous variants are explained by the relatively large number of mutations it has acquired, with 60 mutations not found in the original virus arising from Wuhan, China.
Among these mutations are 32 genetic changes in the spike protein. The spike protein is the part of the virus it uses to attach to human cells, as well as the target of the immune response against the virus, from both vaccines and prior infection.
BA.2 shares many of these same mutations as the original Omicron variant, but also has 28 unique genetic changes of its own. Four of these genetic changes are in the spike protein, which explains why some of its characteristics are different to the original Omicron variant (BA.1), including the fact it appears to be approximately 30 to 50% more infectious than BA.1.
Just as we have seen new variants arise, followed by the evolution of subvariants or different lineages, the SARS-CoV-2 virus has continued to change in other ways as well. In recent times we have seen not just spontaneous changes in the genetic code that have accounted for the changes described above, but also so-called recombinants.
A recombinant is where related viruses exchange genetic material to create offspring with genetic material from both parent viruses. This can arise when viruses of two different strains (or variants or subvariants) co-infect the same cell.
of the viruses can get mixed and packaged together to make a new recombinant virus, with properties of either or both parent viruses. The properties of the recombinant virus therefore depend on which parts of the genetic material from the parent viruses make it into the new version just like you might have your mum’s nose and your dad’s knees.