The World Health Organisation bristles at quarantines shorter than 14 days. But the Swedish approach is to have measures that people can live with for at least a year, says Dr Carlson, because there is no vaccine yet. The goal is to stop as much transmission as possible without unduly disrupting people’s lives, especially in ways that harm their mental or physical (not to mention economic) health. Transmission happens most easily within households, and people are most contagious in the first week after they are infected. So Sweden’s quarantine policy could stop the bulk of covid’s spread—as long as people comply.