School Closures due to Seasonal Influenza: Experience from Eleven Influenza Seasons - United States, 2011-2022

While there are numerous studies about influenza pandemic-associated school closures, literature is scant regarding closures associated with seasonal influenza. To address this knowledge gap, we conducted systematic daily online searches from August 1, 2011- June 30, 2022, to identify public announcements of unplanned school closures in the US lasting [≥]1 day, selecting those that mentioned influenza and influenza-like illness (ILI) as reason for school closure (ILI-SCs). We studied ILI-SC temporal patterns and compared them with reported outpatient ILI-related healthcare visits and laboratory confirmed influenza hospitalizations with attention to the difference between the pre-COVID-19 pandemic and the COVID-19-affected years. We documented that ILI-SCs occurred annually and concurrently with, and likely as a consequence of, widespread illness. The strongest correlations were primarily observed during influenza A (H3N2)-dominant seasons. ILI-SCs were heavily centered in HHS Region 4 and disproportionately impacted rural and lower-income communities. Article summary lineInfluenza-related school closures occurred annually in the US and their temporal patterns mirror the general patterns of influenza activity on both national and regional levels as observed through routine surveillance of medically attended ILI.