Using Absentee Data to Enhance Syndromic Surveillance in Miami-Dade County, 2007

Purpose To describe the utility of school absentee data to enhance syndromic surveillance activities for outbreak detection. Methods Miami-Dade County Health Department receives daily electronic, raw data from all public schools that contains student demographic and geographic information. The percentage of absenteeism was estimated by age group with table and trend figures. Criteria selected at which an alert is raised for absenteeism was set as 8%. SAS, Microsoft Access, and ArcGIS were used to perform data analysis and create reports with a geocoded map of the schools with absentee rates at or above 8%. Results On March 11th a large festival took place in Miami-Dade County. In the days following, an analysis of the Electronic Surveillance System for the Early Notification of Community Based Epidemics (ESSENCE) and public school absentee data signaled a spike in the numbers of chief complaints for gastrointestinal illness (GI) at the emergency rooms (ERs) and in the absences in the public school system. The March 12th alerts for GI were observed on ESSENCE among the 0–4, 5–17, and All age groups. Coincidentally, 108 schools had an absentee rate at or above 8%. The monthly average for the number of schools with an absentee rate at or above 8% is 40 (Range: 25–57). Schools with absentee rates at or above 8% for March 12th matched the zip codes of patients visiting the ER for GI. Forty percent (66 of 165) of children aged 0–17 visited the ER March 11th in the evening. On March 12th a similar trend was also observed. Conclusion Further investigation revealed many cases visited the ER during the evening hours on March 11th and 12th. This observed delay to visit the ER may signal that the GI cases were not severe in nature since many parents took their children to the ER later in the day. School absentee data has been used to support other surveillance activities which include detecting chemical and biological attacks and most commonly, early disease outbreaks. However, in practice the data has a limitation; the reason for absence is unknown. Surveillance efforts including school absentee data are useful when enhanced with other surveillance systems.