Dr. Peter Hotez, director of the Center for Vaccine Development at Texas Children’s Hospital, calls these many new lineages “Scrabble variants” because they contain letters like X and Q that get high scores in the game.The new variants descend from slightly different branches of the Omicron family tree, but they have evolved to share some of the same changes in their genomes that help them slip past our immunity against the virus.At the beginning of October, each one accounted for about 1% of new infections in the United States, but they have been roughly doubling in prevalence each week.BQ.1.1 is now causing about 1 in 5 new Covid-19 infections in the Northeast, where cases and hospitalizations are rising.In a statement released Friday, the World Health Organization’s Technical Advisory Group on SARS-CoV-2 Virus Evolution said the most mutated families of the rising subvariants – XBB and BQ.1 – aren’t different enough from Omicron to be considered separate variants of concern."