What worries scientists globally is that CH.1.1 has now acquired a Delta mutation, which could make it more pathogenic. Dr. Sanjay Pujari, a member of the national Covid task force, told TOI: ‘An R mutation, proposed to be associated with increased cell fusion and pathogenicity in animal models, is hypothesized to explain the severe disease associated with the Delta variant that has been identified in CH .1.1 sequences However, pathogenicity in Delta may be a property of other mutations and interactions between them and has not yet been understood.
Dr. Pujari said, “Furthermore, the Delta wave occurred when the immune wall was inadequate. More data are needed before any increased pathogenicity properties can be attributed to CH.1.1.” A senior INSACOG official told TOI that India so far had nothing to worry about as cases continued to decline in the country and even in Maharashtra (where most of the CH.1.1 samples came from).
“The sub-variant is nothing unusual as it is descended from Omicron’s BA.2.75. Most of the Covid test numbers are currently for patients attending healthcare facilities and low community level testing. A constant check on the spread of Covid and the current picture does not show an increase in transmission.”
He said India had an average of 200-250 Covid cases per day over the past decade, which is quite a low number. “On both measures of Covid, such as severity and the number of deaths, there does not appear to be any increase,” she said.
CH.1.1 independently acquired the same set of key mutations as BQ.1.1, a more pathogenic descendant of BA.5. However, CH.1.1 is still a descendant of the Omicron mild subvariant BA.2, which is intriguing international scientists.
According to international scientists closely following the SARS-CoV-2 mutations, CH.1.1 is one of the most immuno-evasive variants, and now detected Delta’s R mutation in some samples overseas.
The INSACOG official, however, said: “In 2020-21, when Delta appeared with its key mutations, the community in India was not immunogenically prepared for it. However, now after vaccinations and recurring Covid infections , the population has acquired immunity.”
He said the way subvariants like BA.5 and BQ.1.1 performed in the US was different from their impact in India, which had been almost negligible in terms of spread or severity.
“Population immunity levels, due to exposure and vaccination in each country against emerging subvariants of SARS-Cov-2, differ because there have been different subtypes dominating different geographic areas. Therefore, there are differences in protection at the community level against new sub-lineages in India compared to other countries. The public health impacts of new variants and sub-lineages need to be monitored,” the official added.
