The delta variant is the most dangerous SARS-CoV-2 mutation yet

BUSINESSES IN ENGLAND had been eagerly anticipating June 21st—the “freedom day” when all coronavirus restrictions were to be lifted. But on June 14th Boris Johnson, Britain’s prime minister, dashed their hopes. It was “time to ease off the accelerator” he said. Cases, hospitalisations and admissions to intensive care were rising. Ireland, France and Germany are among countries that have tightened restrictions on travellers from Britain. The cause for concern is the delta variant of SARS-CoV-2 (the virus which causes covid-19).

Previously known as B.1.617.2, the variant was first discovered in India in February, where it contributed to a horrific wave of infections which started in the spring: The Economist estimates that there have been more than 1m covid deaths in India this year. The delta variant has spread rapidly across borders, too. According to GISAID, a data-sharing initiative for corona- and influenza-virus sequences, the mutation has been identified in at least 70 countries. It seems to be the most prevalent SARS-CoV-2 strain in places including Canada, Indonesia, Pakistan, Portugal and Russia. Britain was slow to close its borders to travellers from India after the new variant was detected there; as a consequence the variant has spread more quickly than it might otherwise have done.