The Brihanmumbai Municipal Corporation (BMC), Mumbai’s civic body, on April 6 announced that a case of the XE variant of the coronavirus had been confirmed in the city, based on the initial genomic analysis of a sample collected from a South African national on February 27.
Within hours, the Union health ministry rejected the report, saying that the Indian SARS-CoV-2 Genomics Consortium (INSACOG), a network of laboratories involved in genomic surveillance of Covid-19 viruses, had not confirmed it yet.
However, scientists associated with the crucial project point out that it may only be a matter of time before the presence of the variant, with properties of both the BA.1 and BA.2 sub-types of Omicron, is established in India, if it has been confirmed in other countries.
They also say that what really matters is whether XE has a growth advantage over other variants and its impact on local epidemiological and disease patterns.
What is the XE recombinant variant?
The XE recombinant variant, which combines two different Omicron strains—BA.1 and BA.2—was first identified in the UK on January 19.
Officials in the UK Health Security Agency and the World Health Organization say that early data suggests it may be the fastest-spreading variant yet, almost 10 percent more transmissible than BA.2 (which is more transmissible than BA.1). They also say that it is too early to determine how much of a threat it can pose to public health.
Importantly, the WHO has not categorised XE has a Variant of Concern (VoC) as yet.
A majority of the genome in this recombinant variant includes the S gene belonging to BA.2. However, it also has some properties of the BA.1 sub-type.
As per a bulletin released by the WHO on April 1, about 600 sequences of the virus had been confirmed in the UK.
What we do not know yet
Scientists are yet to establish the exact rate of transmission of the XE and whether it is capable of leading to different disease characteristics, including severity, as compared to other Omicron variants.
The variant is being closely monitored by WHO and scientists in several countries for any associated public health risk.
“The things that really need to be understood are what survival and transmission advantage would XE have vis a vis other Omicron sub-variants and whether its virulence has changed,” said a senior scientist associated with INSACOG.
How much should India worry?
A top scientist with the Indian Council of Medical Research-National Institute of Virology (ICMR-NIV) said “the variant is being closely monitored”.
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Senior virologist Dr Shahid Jameel stressed that given that the XE is a mixture of BA.1 and BA.2 and that almost all Indians have antibodies to SARS-CoV-2 by way of prior infection or vaccination, it may not make any significant difference to India.
“Recombinant variants are not unusual. The key is whether it has any growth advantage over its parent strains,” said Jameel, who is a fellow at Green Templeton College, University of Oxford, UK, and a visiting professor at Ashoka University. “There isn’t clear evidence on that, according to the latest UKHSA report.”
Public health expert Dr Chandrakant Lahariya said the XE does not need the attention it seems to be getting.
“The Omicron wave in the whole of Europe was largely driven by the BA.1 variant, which explains why Covid-19 cases in parts of the UK may be rising as the BA.2 variant or probably XE variant (which is very similar to BA.2) now seems to be spreading,” he said. “However, I do not see a reason for India to worry as the Omicron wave here was dominated by the BA.2 sub-variant already.”
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