BACKGROUND: Enteric disease outbreaks are substantial public health problems. The Pennsylvania Department of Health (PADOH) as well as county and municipal health departments in Pennsylvania report information on enteric outbreaks to the National Outbreak Reporting System (NORS), a web-based platform launched by CDC in 2009. This report summarizes NORS data submitted by Pennsylvania jurisdictions from 2009–2014.
METHODS: An outbreak is generally defined as two or more cases of a similar illness epidemiologically linked to a common exposure. Data submitted by Pennsylvania investigators to NORS were downloaded from the NORS website and imported into SAS 9.4. Information recorded for each outbreak includes the number of associated cases, outbreak setting, etiologic agent, implicated food vehicle, and many other factors. A descriptive analysis was performed using SAS 9.4.
RESULTS: From 2009 to 2014, a total of 1,176 enteric outbreaks were reported to NORS. These outbreaks comprised 39,328 cases of illness and included 751 hospitalizations and 36 deaths. The number of reported outbreaks annually increased from 2009 (n=143) to 2013 (n=277), but decreased to 179 in 2014. Timeliness of reporting, as measured by median days from first illness onset to entry into NORS, improved each year, from 45 days in 2010 to 24 days in 2014. Norovirus was the most common cause of outbreaks (466 outbreaks, or 40% of the total), and norovirus outbreaks tended to be large, having an average of 49 cases/outbreak. Etiology was undetermined for 34% of outbreaks. Salmonella and Campylobacter caused 8% and 6% of outbreaks, respectively. The most common primary transmission mode was person to person (65% of outbreaks), followed by undetermined mode (22%), foodborne (11%), and animal contact/environmental (1%). Among the 129 foodborne outbreaks, exposure occurred at a restaurant in 38% of outbreaks and in a home setting in 16%. Transmission setting could not be determined for 19% of foodborne outbreaks. Most reported norovirus outbreaks (75%) occurred at long-term care facilities.
CONCLUSIONS: Information from the NORS system can be useful in analyzing trends, outbreak settings, and routes of transmission. Findings, such as identifying that long term care facilities had a high percentage of norovirus outbreaks, can be used to formulate primary and secondary prevention measures.