Colorized scanning electron micrograph of a cell infected with the Omicron strain of SARS-CoV-2 virus particles (pink), isolated from a patient sample. Image captured at the NIAID Integrated ...

Two new fast-spreading subvariants of Omicron are causing fresh surges of Covid around the world. BA.4 and BA.5 were first identified in South Africa and may soon become the dominant strains in ...