The 2019–20 flu season basically didn’t happen. Same for a couple other respiratory viruses. But that could make future seasons worse.
AS AUTUMN FADED to winter last year, a few infectious disease researchers started turning their attention away from the Covid-19 pandemic and back to something more familiar. This was the time of year they’d ordinarily start looking at their numbers for influenza, the seasonal flu—to see how bad the outbreak would be, and to assess how well that year’s vaccine dealt with the protean respiratory virus.