Evaluation of the 2009-2010 Pennsylvania Influenza Sentinel School Monitoring System

BACKGROUND: The 2009 pandemic influenza A (H1N1) disproportionately affected school-aged children. School absence records have been suggested as a tool for influenza surveillance. Therefore, for the 2009-2010 school year, the Pennsylvania Department of Health established a voluntary sentinel network of elementary (ES), middle (MS) and high schools (HS) around the state to report data on: 1) school absenteeism, and 2) visits to the school nurse for influenza-like illness (ILI).

METHODS: Participating schools provided baseline numbers of students and grades. Daily absenteeism and ILI data were submitted by the schools on a weekly basis through an online survey. Participation and weekly response rates were used to determine overall acceptability and representativeness. Data from the monitoring system were compared to statewide reports of laboratory-confirmed influenza.

RESULTS: Approximately 11% (367/3244) of public schools were enrolled in the system (ES, n=214; MS, n=69; HS, n=84). These schools represented 19% of the state's 500 school districts and covered 12% of PA students (214,685/1,790,000; ES, n=91,525; MS, n=44,168; HS, n=78,992). A mean of 84% of enrolled schools (range 62-92%) completed the survey each week. Absenteeism was highest during the week ending on October 30th, when 36% of schools reported elevated levels of absenteeism. The peak week of absenteeism coincided with the peak of statewide laboratory confirmed influenza cases.

CONCLUSIONS: The school-based sentinel absenteeism network proved to be an easily established system for monitoring influenza patterns in school-aged children. Further analyses are necessary to determine the correlation and comparative value of such a system and other influenza surveillance systems.