Enhancement of sentinel surveillance for influenza-like illness through electronic medical record data aggregation and GIS-mapping by community in Williamson County, Texas

Background: Williamson County and Cities Health District (WCCHD) collects voluntary information from a variety of sentinel provider sources on both laboratory-confirmed influenza and incidences of influenza-like illness (ILI).  Lone Star Circle of Care (LSCC) is a Federally Qualified Health Center whose headquarters are in Williamson County.  Methods:  Using SQL database programming, LSCC extracted data from its electronic medical record (EMR) to identify patients presenting with symptoms meeting the definition of ILI.    From June 2012 to September 2013 LSCC submitted weekly reports to WCCHD which included data on total patient visits and visits due to ILI.  Data were aggregated by zip code, sex, age group, and pregnancy status.  WCCHD aggregated zip code data into five “communities” and mapped relative severity of ILI (minimal to intense) in each community using ArcGIS.  Results:  Age distribution of LSCC patients differed from the general population of Williamson County with a significant shift to the pediatric population. ILI encounters  occurred primarily in the pediatric population (1-17 years of age).  Rural areas of the county were the first to reach a moderate level of ILI in week 39 of 2012, and the last to experience moderate ILI at the end of the season in week 15 of 2013.  Throughout the 2012-2013 influenza season, ILI incidence was minimal in women aged 18-49 years (301 ILI visits in 37,193 total encounters), and it was exceptionally low in those who were pregnant (only 12 ILI visits in 11,527 total obstetric encounters). Aggregated LSCC EMR data was found to be a useful tool for local community and population-level situational awareness throughout the influenza season.