New Covid variant XBB.1.5 is ‘most transmissible yet’ warns World Health Organisation Posted on January 5, 2023 By Charlielikes The new Covid subvariant XBB.1.5, which has seen a rise from 4% to 41% of US infections during December, is the “most transmissible yet” warned the World Health Organisation news Tags:‘new, 'is, ‘most, ‘world, covid, health, news, organisation, topnews, transmissible, trending, variant, warns, xbb.1.5, yet