F OR MUCH of 2020 the covid-19 virus was, in genetic terms, a little dull. Early in the pandemic a version of SARS- Co V-2 that was slightly different from the one originally sequenced in Wuhan, and spread a bit better, came to dominate the picture outside China. But after that it was just a case of a letter or two of genetic code changing here and there. Sometimes such mutations proved useful for working out where infections were coming from. But none of them seemed biologically relevant. By September Salim Abdool Karim, a South African epidemiologist, was beginning to find his monthly updates on new mutations “quite boring”. He considered dispensing with them altogether.