World Health Organization officials confirmed on Wednesday that a new sub-lineage of the Omicron variant — classified as the BA.2.75 — appears to be growing in India, where it was first found.
“In Europe and America, BA.4 and BA.5 are driving waves. In countries like India, a new sub-lineage of BA.2.75 has also been detected, which we’re following,” WHO’s director-general Tedros Adhanom Ghebreyesus said at a virtual press conference late on Wednesday.
WHO chief scientist Soumya Swaminathan, in a separate
World Health Organization officials confirmed on Wednesday that a new sub-lineage of the Omicron variant — classified as the BA.2.75 — appears to be growing in India, where it was first found.
“In Europe and America, BA.4 and BA.5 are driving waves. In countries like India, a new sub-lineage of BA.2.75 has also been detected, which we’re following,” WHO’s director-general Tedros Adhanom Ghebreyesus said at a virtual press conference late on Wednesday.
WHO chief scientist Soumya Swaminathan, in a separate video, said the BA.2.75 was “first reported from India and then from about 10 other countries.” There are, she added, still limited sequences available, “but this sub-variant seems to have a few mutations on the receptor-binding domain of the spike protein…a key part of the virus that attaches itself to the human receptor”.
Also read: Covid claims life of 9-month-old, youngest this year in city
“So we have to watch that. It’s still too early to know if this sub-variant has properties of additional immune evasion or indeed of being more clinically severe. We don’t know that,” she said.
The WHO’s Technical Advisory Group on Sars-CoV-2 Virus Evolution (TAG-VE) will now analyse the signs further and decide if this lineage requires a Variant of Concern (VOC) classification of its own.
HT reviewed realtime tracking data from the global coronavirus genome repository GISAID and discussions between virologists to piece together the early clues and the concerns they indicate.
First key signal: Mutations
The sub-lineage first caught attention of scientists in late June when they noticed particular mutations that appear to be a location in the virus that is informally described as the “supersite” for antibody binding: the N terminal domain, or NTD. This mutation, among nine unique to the BA.2.75, is classified as G446S, and scientists believe it could reduce the ability of antibodies exposed to other configurations of the virus to recognise this one, thereby making it more resistant. “G446S is at one of most potent sites of escape from antibodies elicited by current vaccines that still neutralize BA.2,” wrote Jesse Bloom, who heads one of the virology research labs at the Fred Hutch research centre, in a tweet last week.
Also read: India adds 18,930 Covid cases in last 24 hrs; active caseload nearing 1.2 lakh
The assumption from this is that immunity from vaccines or early infections is likely to be less potent when faced with the BA.2.75.
Second concern: Growth rate
Genome sequences submitted to the GISAID database suggest the variant’s footprint is growing in India, where it was first found in early May. As on Thursday, there are 92 sequences submitted from around the world that can roughly be classified as belong to BA.2.75 (there isn’t a formal BA.2.75 classification on GISAID yet, which is why researchers are using a custom query to find this lineage). Of the 92, 73 are from India — and of these, 18 were collected in the past fortnight alone.
To understand how it has grown, BA.2.75 samples accounted for less than 1% of all samples submitted to GISAID in the first half of June, but that proportion grew to over 10% in the second half of June, a cov-spectrum.org query showed. An important caveat here is that this could because a state with more infections of this lineage may have submitted more samples in the second half of June than a state where this virus was still to reach. Nonetheless, the numbers are significant enough to suggest a transmission advantage over older BA.2 lineages that are at present the most widespread in India.
More clues needed
The highest number of samples, 50, appear to be from Maharashtra, a state that has not shown any worrying uptick in hospitalisations or deaths, or even a particularly rapid surge. What scientists will now watch for is if the nine mutations confer the variant any additional trait, particularly severity that has largely not been a concern with the Omicron family of the coronavirus till now. It also remains to be seen how this sub-lineage competes with the BA.4 and BA.5 sub-lineages, which are causing new waves of infections in parts of Europe and US.
One Subscription.
Get 360° coverage—from daily headlines
to 100 year archives.
Archives
HT App & Website