Purpose: A multi-agency investigation was conducted to characterize the outbreak, identify and remove contaminated product from the market and recommend long-term prevention measures.
Methods: Public health investigators defined and interviewed cases, collected food specimens from case homes and conducted descriptive analyses to identify hypotheses. Federal food safety investigators led systematic traceback investigation of six hypothesized food sources. Federal, provincial and local food safety/public health agencies conducted inspections of implicated facilities. Food and environmental specimens were collected and analyzed at provincial and federal laboratories. E. coli O157:H7 isolates were identified using routine culture methods and were characterized by pulsed field gel electrophoresis (PFGE) and multi-locus variable number tandem repeat analysis (MLVA).
Results: This outbreak resulted in 119 illnesses including 22 (18.5%) hospitalizations and 6 cases of hemolytic uremic syndrome. Symptom onsets ranged from July 20 to October 6, 2014. The majority of cases reported consuming dishes containing pork at Asian-style restaurants in two geographically distinct cities during their exposure period. The outbreak strain, defined by sixteen PFGE patterns, was isolated from food and environmental specimens, including a pork carcass, whole pork cuts, finished products, and food and non-food contact surfaces.
Significance: Contaminated pork products produced and distributed in Alberta, Canada, were the source of the outbreak. Contamination of this novel vehicle persisted through cooking. The systematic approach used in the traceback investigation was effective in the absence of a leading hypothesis. The complexity of food distribution networks and impact of poor invoicing on ability to take action were highlighted.
Note: Preparation of the final outbreak investigation report is ongoing. If accepted, results reported in the abstract will be adjusted.