Contribution of sentinel surveillance sites to San Diego County's influenza surveillance program

The County of San Diego (COSD) conducts influenza surveillance utilizing multiple data sources. Medical community partners are encouraged to report influenza detections in order to describe the impact of influenza and characterize predominant circulating viral strains. To enhance laboratory detection and reporting of influenza during the 2006-07 season, COSD purchased rapid influenza tests and recruited 14 community clinics and student health centers to be sentinel testing sites (STS). STS were provided with Quidel® QUICKVUE rapid influenza A+B tests. Sites logged patient data and test results and faxed data to Public Health. Some also submitted patient specimens to Public Health Laboratory (PHL) for viral isolation and subtyping. Of the 14 STS, 8 reported influenza positive test results, representing 15% of the total reports from all sources. STS reports peaked during week 5, consistent with all other reporters, but dropped off sharply at week 8 while other reporters continued to report cases for several more weeks. 14 STS patient specimens were culture-confirmed and subtyped at public health laboratory, representing 13% of all influenza A/H1 and A/H3 subtypes identified during the season. STS were a valuable addition to COSD's influenza surveillance in 2006-07, contributing to influenza diagnoses and subtypes identified. STS case reporting correlated with seasonal influenza peak activity. Incorporating STS enhanced influenza detection and reporting among (typically uninsured) patients seeking care at community clinics and student health services, and strengthened public health's relationship with these important community partners.