Four cases of Omicron subvariant BF.7, apparently the strain driving China's current surge of Covid cases, have been detected in India so far. In the Covid review meeting chaired by Union Health Minister Mansukh Mandaviya on Wednesday, experts said although there is no overall increase in Covid caseload as of now, there is a need for continued surveillance to keep a track of existing and emerging variants. So, what is the threat of this new strain?