Effectiveness of a school district closure for pandemic influenza A (H1N1) on acute respiratory illnesses in the community: a natural experiment

Background. Following detection of pandemic influenza A H1N1 (pH1N1) in Dallas/Fort Worth, Texas, a 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.