Establishing criteria to initiate enteric outbreak investigations in British Columbia

Objective: To establish and evaluate criteria to initiate provincial enteric outbreak investigations based on characteristics of alerts, clusters and successful outbreak investigations. Methods: We tracked all enteric disease alerts and clusters reported to the British Columbia Centre for Disease Control (BCCDC) in 2011 and 2012. Information was collected on etiology, number of cases, geographic spread, dates reported, and method of notification. Actions were classified as no further action, review/report or investigation. Outbreak investigation outcome was classified as solved/not solved. 2011 data were used to identify characteristics of alerts and clusters more likely to lead to outbreak investigations and of solved outbreaks to establish criteria. Criteria for initiating an outbreak investigation were evaluated retrospectively using 2011 data and then implemented in 2012. Results: In 2011, 251 alerts/clusters of enteric diseases were reported. Fourteen (5.6%) led to an outbreak investigation and nine (64.3%) of the outbreaks were solved. Analyzing the data retrospectively, criteria were identified from the alerts and clusters that led to outbreak investigations and successful outbreak investigations: pathogen specificity, timely notification, a common source or event, and multi-regional outbreaks or outbreaks reported by other agencies. After applying these criteria prospectively in 2012, we took action on a smaller proportion of the 244 alerts and clusters (32.0% compared to 44.6% in 2011) and 66.7% of them were solved (compared to 64.3% in 2011). Conclusion: Continued evaluation will identify whether this will improve outbreak investigations and use of resources in British Columbia.