Nearly 80% of Covid-positive samples sent for genome-sequencing by laboratories in the city have been found to contain the BA.2 sub-lineage of the Omicron variant, nicknamed the 'stealth version', as it cannot be picked up in RT-PCR tests and requires genome-sequencing.

from Times of India https://timesofindia.indiatimes.com/city/kolkata/ba-2-stealth-variant-makes-up-80-of-kolkatas-o-infections/articleshow/88821640.cms