Summary of 11 years of enteric outbreak investigations and criteria to initiate an investigation, Province of Quebec, 2002 through 2012.

This article presents a retrospective analysis of enteric disease outbreak investigations led by or conducted in collaboration with provincial health authorities in the Province of Quebec from 2002 through 2012. Objectives were to characterize enteric disease outbreaks, quantify and describe those for which a source was identified (including the control measures implemented), identify factors that contributed to or impeded identification of the source, and recommend areas for improvement in outbreak investigations (including establishment of criteria to initiate investigations). A descriptive analysis of enteric disease outbreak summaries recorded in a provincial database since 2002 was conducted, and corresponding outbreak reports were reviewed. Among 61 enteric disease outbreaks investigated, primary pathogens involved were Salmonella (46%), Escherichia coli O157:H7 (25%), and Listeria monocytogenes (13%). Sources were identified for 37 (61%) of 61 of the outbreaks, and descriptive studies were sufficient to identify the source for 26 (70%) of these. During the descriptive phase of the investigation, the causes of 21 (81%) of 26 outbreaks were identified by promptly collecting samples of suspected foods based on case interviews. Causes of outbreaks were more likely to be detected by weekly surveillance or alert systems (odds ratio = 6.0, P = 0.04) than by serotyping or molecular typing surveillance and were more likely to be associated with a common event or location (odds ratio = 11.0, P = 0.023). Among the 37 outbreaks for which causes were identified, 24 (65%) were associated with contaminated food, and recalls were the primary control measure implemented (54%). Review of enteric outbreaks investigated at the provincial level in Québec has increased the province's ability to quantify success and identify factors that can promote success. Multiple criteria should be taken into account to identify case clusters that are more likely to be resolved.

Multiple outbreaks of gastroenteritis that were associated with 16 funerals and a unique caterer and spanned 6 days, 2011, Québec, Canada.

In January 2011, multiple acute gastroenteritis outbreaks that spanned many days and were related to attendance at funerals were reported to public health units in Quebec. An epidemiological investigation was initiated to identify the source of the contamination and to explain the extent of the contamination over time. Thirty-one cohorts of individuals attended different funerals held between 14 and 19 January. All attendees were served a cold buffet made by the same caterer. Of these 31 cohorts, 16 (with a total of about 800 people) contained individuals who reported being ill after the funeral. Symptoms were mainly diarrhea (89 to 94% of individuals), vomiting (63 to 90%,) and fever (26 to 39%), with a median incubation period of 29 to 33 h and a median duration of symptoms of 24 to 33 h, suggesting norovirus-like infection. Among the 16 cohorts, 3 were selected for cohort studies. Among those three cohorts, the mean illness rate was 68%. Associations were found between those who fell ill and those who had consumed pasta salad (relative risk [RR] = 2.4; P = 0.0022) and ham sandwiches (RR = 1.8; P = 0.0096). No food handlers reported being sick. No stool samples were provided by individuals who became ill. Environmental and food samples were all negative for causative agents. Although the causative agent was not clearly identified, this investigation raised many concerns about the importance of preventing foodborne transmission of viral gastroenteritis and generated some recommendations for management of similar outbreaks.