Scientists probing spike in cases look at Omicron sub-variant


As scientists continue to probe the possible causes for the recent rise in Coronavirus cases in the country, the BA.2.75, one of the several sub-variants of the parent Omicron variant, is under the spotlight.

The BA.2.75, belonging to the BA.2 sub-lineage which was the dominant strain in India earlier this year, has been found to have an 18 per cent growth advantage over the other currently circulating Omicron sub-variants.

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Dr Rajesh Karyakarte, microbiologist at Pune’s B J Medical College and head of Maharashtra’s genome sequencing effort, said the current surge of cases in the country was a little curious since all the circulating strains are still the sub-lineages of Omicron, and no new variant, different from Omicron, has been detected.

“We already had a pretty large wave driven by the Omicron variant earlier this year. So, the present surge is a little unexpected,” he said.

Karyakarte’s team, and scientists elsewhere, have picked up three sub-variants, BA.2.74, BA.2.75, and BA.2.76, as the possible drivers for the current surge. These three sub-variants have more than nine changes in the spike protein. These three are expected to outnumber the BA.4 and BA.5 sub-variants which were the most common until a few weeks ago.

Mike Honey, a data integration specialist from Melbourne, said in a Twitter post that the BA.2.75 sub-lineage (nicknamed Centaurus) was an “evolutionary jump” from BA.2, the most common Omicron sub-variant in the country until now.

Scientists in India said it (BA.2.75) was now one of the most commonly detected sub-variant in the country in recent results of genome sequencing.

“BA.2.75 has a distinct growth advantage over BA.4 or BA.5,” Dr Karyakarte told The Indian Express.

However, there is no evidence as of now to suggest that the BA.2.75 also causes a more severe form of infection. Karyakarte said clinical studies were being prepared to assess the impact of this infection on the body.

Tom Peacock, virologist at Department of Infectious Diseases, Imperial College, in a tweet, said that scientists need to keep a close eye on BA.2.75 because it has a large number of spike mutations, two of them quite significant, and also because it is being picked from geographically diverse locations.

It is possible that the mutations in the BA.2.75 sub-variant give it an enhanced ability to dodge antibodies and attach itself to human cells. This could result in increased infectivity even among those who have previously been infected, or have been fully vaccinated.

“Just how mutations of SARS-CoV-2 virus are panning out either in mild or dangerous ones is being closely watched,” Dr Karyakarte said.

“We have also asked private laboratories to send samples for genome sequencing and conduct a clinical study to understand the symptoms of people who died, were hospitalised or then were on oxygen support,” he said.

Vinod Scaria, a medical researcher in precision medicine and clinical genomics, however, said the emergence of BA.2.75 was no reason to panic as of now.

“The point to keep in mind is that the variant is continuously evolving and accumulating more mutations and it is too early to jump to any conclusions,” he said in a tweet.





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