Lockdowns and social-distancing measures aimed at slowing the spread of coronavirus seem to have shortened the influenza season in the northern hemisphere by about six weeks.
Globally, an estimated 290,000–650,000 people typically die from seasonal flu, so a shorter flu season could mean tens of thousands of lives are spared. But the net impacts on global health will be hard to unpick against the large number of deaths from COVID-19 as well as other causes in 2020 and beyond. Tracking influenza and other infectious diseases can help to reveal the effectiveness of public-health policies aimed at stopping the coronavirus pandemic.
Seasonal flu cases in the northern hemisphere usually peak in February and tail off by the end of May. This year, unusually, lab-confirmed cases of influenza dropped precipitously in early April, a few weeks after the coronavirus pandemic was declared on 11 March (see ‘Flu season cut short by COVID-19 measures’). The data comes from tests of more than 150,000 samples from national influenza laboratories in 71 countries that report data to FluNet, a global surveillance system.
