A healthcare worker helps a patient to fill out a form before conducting a PCR Covid-19 test at the Lancet laboratory in Johannesburg on November 30, 2021. - A new, heavily mutated Covid-19 variant, dubbed omicron, spread across the globe on Sunday, shutting borders and renewing curbs as the EU chief said governments faced a "race against time" to understand the strain. (Photo by EMMANUEL CROSET / AFP)
