Effectiveness of a School District Closure for Pandemic Influenza A (H1N1) on Acute Respiratory Illnesses in the Community: A Natural Experiment

school district (intervention community, [IC]) closed all public schools for 8 days to reduce transmission. Nearby school districts (control community [CC]) mostly remained open. Methods. We collected household data to measure self-reported acute respiratory illness (ARI), before, during, and after school closures. We also collected influenza-related visits to emergency departments (EDflu). Results. In both communities, self-reported ARIs and EDflu visits increased from before to during the school closure, but the increase in ARI rates was 45 % lower in the IC (0.6 % before to 1.2 % during) than in the CC (0.4% before to 1.5 % during) (RRRDuring/Before = 0.55, P <.001; adjusted ORDuring/Before = 0.49, P <.03). For households with school-aged children only (no children 0–5 years), IC had even lower increases in adjusted ARI than in the CC (adjusted ORDuring/Before = 0.28, P <.001). The relative increase of total EDflu visits in the IC was 27 % lower (2.8 % before to 4.4 % during) compared with the CC (2.9 % before to 6.2 % during). Among children aged 6–18 years, the percentage of EDflu in IC remained constant (5.1 % before vs 5.2 % during), whereas in the CC it more than doubled (5.2 % before vs 10.9 % during). After schools reopened, ARI rates and EDflu visits decreased in both communities. Conclusions. Our study documents a reduction in ARI and EDflu visits in the intervention community. Our findings can be used to assess the potential benefit of school closures during pandemics