The Omicron subvariant XBB has already acquired more mutations and split into even fitter strains, scientists told TOI on Monday. Till October, India had 71 confirmed cases of XBB-driven Covid infection. The number jumped to 136 on October 23. On Monday, case count was at 235. From the XBB group, Indian scientists said XBB.3 has been responsible for the most infections (63%).