Measures to prevent the spread of covid-19 have also fended off flu

IN SEPTEMBER 2020 doctors and public-health officials in the northern hemisphere were on high alert. They did not know how covid-19 would behave in the first winter of the pandemic. Respiratory viruses tend to surge during cold weather. And there were the usual concerns about influenza, the shape-shifting virus that sickens and kills many people every year. At worst, doctors feared they would see simultaneous outbreaks of covid-19 and flu which would overwhelm hospitals and send deaths soaring—a “twindemic”.