Characterization of the 2009 influenza pandemic using absenteeism data collected with a school-based surveillance system in Erie County, NY
MetadataShow full item record
In late spring 2009, a novel influenza virus emerged and spread quickly across the globe resulting in the declaration of a pandemic in June 2009. Early on, researchers observed notable increases of influenza-like illness (ILI) in school-age children and since these young people were uniquely susceptible to infection with the virus, school absenteeism was hypothesized to be an indicator of pandemic influenza activity in the community. The aim of this study was to determine whether absenteeism was associated with community circulation of influenza during a pandemic and whether this relationship differed among subgroups of the study population. Local school districts collected information on all-cause absenteeism and submitted data daily to the Erie County Department of Health. This study focuses specifically on weeks 40 through 51 of 2009 (10/5 through 12/25/2009), which correspond to the second wave of the influenza pandemic. Cross-correlation analyses were conducted to determine the lag or lead time that maximally correlated weekly average absenteeism rates, in all school districts, or in subgroups, with community-level indicators of pandemic influenza activity. Mean weekly absenteeism rates had the greatest correlation with community-level indicators of pandemic influenza activity with a lead time of one week, suggesting that all-cause absenteeism from a given week predicted pandemic influenza activity one week later. In subgroup analysis, elementary and middle school absenteeism were more strongly correlated with pandemic influenza activity than was high school absenteeism. Therefore, future school-based surveillance efforts for pandemic influenza could focus solely on absenteeism of younger schoolchildren to reduce the burden associated with the surveillance system. We conclude that a school-based surveillance system using all-cause absenteeism was an appropriate surveillance tool during the 2009 influenza pandemic.