The next Covid variant to emerge is poised to be more severe than the mild strains that are currently world-dominant, according to a new study. The ultra-infectious Omicron strain emerged almost exactly a year ago and its mutated spinoffs have risen to the top in virtually every country in the world. They are far milder than the older versions of the virus and many researchers believed they represented a kind of end game for Covid’s evolution, which like many viruses before it, mutate to be more mild so they can spread more easily. But researchers in South Africa say the...