XBB set to be dominant Covid strain, cases double in just 1 week

PUNE: Covid infections caused by Omicron's newly identified XBB have nearly doubled in the last one week in India, experts said, adding that it's now likely the recombinant will become the dominant subvariant in the country within a month.

XBB was seen in 71 cases till October 14 but went up to 136 on October 23. Eight states have reported XBB in their samples: Tamil Nadu (52 cases), Orissa (35), West Bengal (17), Maharashtra (17), Delhi (6), Karnataka (6), Gujarat (2) and Rajasthan (1).

Scientists with India's genome surveillance network said that BA.2.75 is still in the lead but fast losing that position.

BA.2.75 prevalence in samples is down to 70%, from 88% last week. In September, this subvariant was responsible for 93% of India's Covid infections.

"Going by the speed with which XBB is moving ahead and reducing the share of BA.2.75, it seems it will become the dominant subvariant in India within a month. Most of the samples sequenced in the latest run in West Bengal and Delhi had only XBB in them," said a senior INSACOG scientist.

Possibly the most immune-evasive SARS-CoV-2 subvariant to date, according to experts and the WHO, XBB has been detected in 26 countries so far.

In Singapore and Bangladesh, it has already triggered new Covid-19 surges. Canada, England and India are starting to report a rise in XBB infections, according to data from GISAID, an international research organisation that is tracking changes in the virus.

Dr Rajesh Karyakarte, state coordinator for genome sequencing in Maharashtra said: "GISAID data shows the largest concentration of XBB and its spinoff variants in Singapore, followed by India, Bangladesh, the United States, Australia and Denmark. The way this recombinant is moving in India, it is bound to leave other Omicron subvariants behind."

Experts said XBB is now in competition with fellow Omicron spawn BQ.1.1 for the title of the "most immune-evasive variant so far", surpassing shared ancestor BA.5, which was dominant worldwide during the summer. A WHO assessment this week, citing laboratory data, indicated XBB could be the most evasive variant yet.

In India, scientists said currently XBB is being detected in some 20% of cases. BA.2 subvariant is in 7% of cases and prevalence of BA.5 is down to less than 3%.

Last week, India detected a BQ.1 infection in a Pune sample. It remains the only detection of the subvariant so far.