Escherichia coli O157:H7 Outbreak Linked to Raw Milk Cheese in Quebec, Canada: Use of Exact Probability Calculation and Case-Case Study Approaches to Foodborne Outbreak Investigation
Source: Journal of Food Protection®, Number 5, May 2012, pp. 812-997 , pp. 812-818(7)
Abstract:The analytical studies used to investigate foodborne outbreak are mostly case-control or retrospective cohort studies. However, these studies can be complex to perform and susceptible to biases. This article addresses basic principles of epidemiology, probability, and the use of case-case design to identify the source of an Escherichia coli O157:H7 outbreak linked to raw milk cheese consumption in Quebec, Canada; a small number of cases with the same pulsed-field gel electrophoresis (PFGE) profile were involved. Between 4 December 2008 and 15 January 2009, a cumulative total of 16 E. coli O157:H7 cases with the same PFGE profile were reported to Quebec public health authorities. Among the first six cases reported, three had consumed raw milk cheese from the same producer (cheese A). Raw milk cheese is consumed by about 2 % of the Quebec population. By using the exact probability calculation, it was found that a significantly higher proportion of E. coli O157:H7 cases (with the specific PFGE profile) than expected had consumed cheese A (P < 0.001). These computations were updated during the course of the investigation to include subsequent cases and gave the same results. A case-case study corroborated this result. This article considers alternative statistical and epidemiological approaches to investigate a foodborne outbreak—in particular with an exact probability calculation and case-case comparisons. This approach could offer a fast and inexpensive alternative to regular case-control studies to target public health actions, particularly during a foodborne outbreak.
Document Type: Research Article
Affiliations: 1: Ministère de la Santé et des Services sociaux, 1075 chemin Ste-Foy, Québec, Province de Québec, Canada G1S 2M1;, Email: email@example.com 2: Agence de la santé et des Services sociaux de la Montérégie, 1255 rue Beauregard, Longueuil, Province de Québec, Canada J4K 2M3 3: Ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec, 200 chemin Ste-Foy, Québec, Province de Québec, Canada G1R 4X6 4: Laboratoire de santé publique du Québec 20045 Chemin Sainte-Marie, Sainte-Anne de Bellevue, Québec, Canada H9X 3R5 5: Institut national de santé publique du Québec, 1000, route de l'Église, Québec, Canada G1V 3V9 6: Agence de la santé et des Services sociaux de la Montérégie, 1255 rue Beauregard, Longueuil, Province de Québec, Canada J4K 2M3, Université de Sherbrooke, Département des sciences de la santé communautaire, 2500 rue de l'Université, Sherbrooke, Province de Québec, Canada J1K 2R1
Publication date: 2012-05-01
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