The BA.5 sub-variant of Omicron has been found in some samples collected from central, south and southeast Delhi between May and June 16, official sources said on June 27.
The findings were discussed at a meeting on June 17 by the Indian SARS-CoV-2 Genomics Consortium (INSACOG), which reviewed the COVID-19 data to check the possibility of any new emerging variant or sub-variant and ascertain the reasons behind the breakthrough infections.
Almost 5 percent of the samples genome sequenced from central and south-east Delhi tested positive for the BA.5 sub-variant and nearly 2 percent of samples from south Delhi showed its presence. Most of the samples were found to have the BA.2 sub-variant of Omicron.
According to experts, BA.5 is highly transmissible but does not lead to severe infection. Sources said a few samples from Delhi that were sent to the National Centre for Disease Control (NCDC) for genome sequencing tested positive for the BA.4 and BA.5 sub-strains of Omicron, which had triggered the surge in the number of cases in January.
They also said two of the 30 samples genome sequenced at the Institute of Liver and Biliary Sciences showed the presence of the BA.5 sub-strain. The samples were sent to the laboratory between June 1 and June 16. "BA.4 and BA.5 are the off springs of BA.2 and BA.1, and they have undergone mutation. The mutation that has happened has given them a more pronounced characteristic of evading the immunity generated by Omicron that had triggered the infection surge in January," Lalit Kant, the former head of the epidemiology and communicable diseases department in the Indian Council of Medical Research (ICMR), said.
He said the mutation has increased the transmissibility of the virus by 10 to 15 times. "If Omicron was faster spreading than Delta, then these are more transmissible. This is the information we have got so far from the work done outside India. In South Africa, it started in January and by March-April, BA.4 and BA.5 replaced the entire original strain. Even in the US and Europe, BA.4 and BA.5 are spreading fast and replacing the previous sub-variants," Kant added.
The senior scientist said the experiences of other countries show that these sub-variants do not cause severe infection or lead to an increase in hospitalisation. These are also able to escape the immunity generated by vaccination. "BA.5 spreads faster and in some cases, it is also replacing BA.4. Vaccinated people fare better than unvaccinated people, but the immunity starts declining six-seven months after immunisation," Kant said.
Delhi has been witnessing a rising number of Covid cases with the single-day figure breaching the 1,000 mark on June 14. The city logged 1,118 fresh cases of the infection on June 14 with a positivity rate of 6.5 per cent and two fatalities. Since then, the national capital has been logging more than 1,000 cases every day barring last Wednesday, when it logged 928 new Covid cases.