Virus mutations down to chance, in more ways than one

The emergence of several, more infectious strains of the novel coronavirus SARS-CoV-2 has worried governments and scientists, who are investigating how and why the virus became more transmissible. Like all viruses, SARS-CoV-2 mutates in order to maximise its survival chances. When it replicates, tiny errors in its genetic coding are introduced. Most of these are inconsequential. But some—as with the virus variants that emerged recently in Britain, South Africa and Brazil—can give the virus a decisive new advantage. “When we keep case numbers high, we are maximising the virus’s opportunities to get into weird situations, that might be rare, and most of them might lead nowhere,” said Emma Hodcroft, epidemiologist at the University of Bern. More cases equal more transmissions, which maximises the chances that a significant mutation will occur, she said. “If we keep case numbers lower, we essentially restrict the virus’s playground.” Wendy Barclay, a virologist at London’s Imperial College, said mutations were a result...