1719Public health response to a school-based norovirus gastroenteritis outbreak: Environmental sampling as a novel investigative tool

Background. Norovirus outbreaks in schools can amplify rapidly through multiple routes of transmission, and have led to campus closures. Ensuring implementation of transmission-prevention measures is challenging in large secondary schools, where exclusion criteria for ill persons may be limited, and sufficient environmental surface disinfection may be difficult to achieve. During a norovirus outbreak in a Dallas County public high school in 2014, supplemental approaches to outbreak control were assessed, including environmental testing. Methods. Students and staff with vomiting or diarrheal illness reported to the health department were interviewed with standardized questionnaires. Exposure surveys were also administered to all 2500 students. A case-control analysis included 300 cases and 600 controls randomly selected from respondents and matched on gender. Data were analyzed using multiple logistic regression with SAS 9.4. Stool samples from cases and environmental surface swabs were tested for norovirus by RT-PCR assay. Results. An overall attack rate of 32% occurred over 4 weeks, with a peak in cases on January 30, the day of initial report to public health. Cases reported vomiting (83%), diarrhea (57.3%), and fever (40.3%). Norovirus genogroups GI (n = 4) and GII (n = 1) were identified in stool samples. Ongoing new cases 5 days following public health notification prompted environmental sampling. Norovirus GI (n = 8) and GII (n = 2) were identified from multiple surfaces, including: door handles, stair rails, computer keyboards, and a water cooler spigot. Numbers of cases declined after enhanced cleaning targeting these fomites. In the casecontrol analysis, significant predictors included: water fountain use (OR = 1.79, p= 0.004); and participation in the dance team (OR = 1.91, p= 0.03) or theater (OR = 1.78, p= 0.02). Conclusion. Customary public health interventions to control norovirus outbreaks can be difficult to implement comprehensively in public secondary schools. Environmental surface testing for norovirus during persistent outbreaks may assist with identification of particular surfaces and previously unrecognized transmission vehicles to target limited school resources for enhanced disinfection. Disclosures. All authors: No reported disclosures.