NEW DELHI: Omicron sub-variant XBB, which has led to a surge in Covid cases in Singapore, and its strains, especially XBB.3, are fast emerging as a dominant sub-variant in India. In India, nine states have reported XBB, and Tamil Nadu tops the list.
According to data from GISAID, an international research organisation that tracks changes in the virus, 380 XBB confirmed cases had been detected in India till Oct 23.
Most XBB sub-variant have been detected in Tamil Nadu, where 175 cases have been recorded, followed by West Bengal (103).
West Bengal was the first state in India, which first detected this most evasive Omicron sub-variant in August. The other states which have confirmed cases of XBB-driven Covid infection are – Odisha (35), Maharashtra (21), Delhi (18), Puducherry (16), Karnataka (9), Gujarat (2) and Rajasthan (1)
Further, of the 380 sequences, XBB.3 was found to be 68.42 per cent – the highest among all the lineages of XBB, the data showed. XBB.2 was 15 per cent, and XBB.1 was 2.63 per cent.
"XBB is moving fast in India and is further evolving fast. Out of all its strains, XBB.3 would dominate in India," Dr Rajesh Karyakarte, who coordinates SARS-CoV-2 genetic sequencing in Maharashtra, told The New Indian Express.
Among the offshoots of the Omicron variant swarming globally and in India and described as a variant soup, XBB – a recombinant of BA.2.10.1 and BA.2.75 sub-lineages - is the dominant sub-variant in India so far.
BQ.1 and other sub-variants are also being detected in India, but not in large numbers. XBB and BQ.1 are both descendants of the highly transmissible Omicron variant.
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"It is clear that XBB is a dominant sub-variant now. It has many immune escape mutations; therefore, it has a growth advantage over other sub-variants. Chances are that it could replace BA.2.75, the dominant Omicron sub-variant in India," Dr Karyakarte said.
XBB has been categorised at level 7, meaning it has many mutations, while BQ.1 is level 5. "This means XBB will have more growth advantage over BQ.1 and one which would replace BA.2.75 in India."
However, the professor in the microbiology department at BJ Government Medical College in Pune, said clinical studies hadn't shown any sudden rise in Covid-19 cases or severity.
"In our clinical study, we didn’t see any severe patients or anyone needing oxygen or found any increase in hospitalisation rates. So far, it hasn't produced any serious diseases in people," he added.
Dr Pragya Yadav, a senior scientist at the Indian Institute of Medical Research (ICMR)-National Institute of Virology (NIV) in Pune, said XBB is emerging in India. Most cases are asymptomatic so far. "We need to wait to see whether it would lead to any severity or hospitalisation as is being seen in Singapore," Dr Yadav said.
XBB, being reported mainly from Asian countries like Singapore, Bangladesh and India, is setting off fresh waves of infection, leading to fear that this could usher in another Covid wave. XBB is also being reported from Australia and South Korea too.
According to a recent article in Nature, XBB looks likely to dominate infections in Asia.
According to the World Health Organisation (WHO), XBB has a global prevalence of 1.3 per cent, and it has been detected in 35 countries.
According to the WHO's Technical Advisory Group on SARS-CoV-2 Virus Evolution (TAG-VE), there has been a "broad increase in the prevalence of XBB in regional genomic surveillance". The technical advisory group met on October 24 to discuss the latest evidence on the Omicron variant of concern and how its evolution is currently unfolding.
The current data have not suggested substantial differences in disease severity for XBB infections; there is, however, early evidence pointing at a higher reinfection risk as compared to other circulating Omicron sub-lineages, the group noted.
The TAG-VE also said that whether the increased immune escape of XBB is sufficient to drive new infection waves appears to depend on the regional immune landscape as affected by the size and timing of previous Omicron waves, as well as the Covid-19 vaccination coverage.
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