Explained | XBB.1.16, the Omicron recombinant behind India’s new COVID spike Premium
The Hindu
Amid the ongoing increase in the number of seasonal Influenza H3N2 cases, an uptick in COVID-19 cases is being seen in India, driven by XBB.1.16.
Over the past three years and multiple waves of infection, SARS-CoV-2 continues to evolve by accumulating genetic variations. Uncommonly, a co-infection of multiple lineages of the virus could result in recombinations between genomes which can give rise to chimeric genomes, otherwise called recombinants.
While most recombinations may not give rise to viable viruses, there is a rare possibility that recombination could result in the creation of a new lineage of the virus with better functional capabilities than either of the parent lineages. Genome sequencing and surveillance of viruses could efficiently identify such recombinants, as they would have the variant complement of two-parent lineages.
Several recombinant lineages of SARS-CoV-2 have emerged during the course of the COVID-19 pandemic. The PANGO network, an international consortium of researchers for naming SARS-CoV-2 lineages, has an established system for identifying and designating recombinants of SARS-CoV-2. Currently, close to 100 recombinant lineages have been designated by the PANGO network, all of which begin with the letter ‘X’, followed by a letter to denote the order of their detection.
Two recombinant lineages of SARS-CoV-2 are currently designated as ‘Variants Under Monitoring’ by the World Health Organization: XBB, a recombinant of Omicron sublineages BA.2.10.1 and BA.2.75, and XBF, a recombinant of BA.5.2.3 and BA.2.75.3 Omicron sublineages.
The lineage XBB.1.5, a sublineage of the XBB first identified in New York City in October 2022, is currently designated as a Variant of Interest (VOI) by the WHO. Tracking Omicron recombinants is important for the early detection of lineages that may have functional advantages over currently circulating variants such as increased transmissibility in populations with prior immunity to the virus.
What is the XBB.1.16 lineage of SARS-CoV-2?
First detected in SARS-CoV-2 sequences from India, the XBB.1.16 is a recombinant lineage of the virus and is a descendent of the XBB lineage. The earliest sequence of this lineage belongs to a viral genome isolated in New York in January 2023 and the lineage has been seen to be circulating predominantly in India.