When they occur, most mutations either kill the virus or cause no change in its structure or behavior. Although improved surveillance and sequencing efforts might partly explain why these variants are appearing now, some repetition in their patterns suggest the mutations are not random. “What we’re seeing is similar mutations arising in multiple places,” says Adam Lauring, a virologist at the University of Michigan. It is unclear, however, whether the variant’s enhanced contagiousness comes from N501Y alone or also involves some combination of other spike protein mutations. Although they share mutations with other newly discovered versions, they appear to have arisen independently of those variants.