Everything but the kitchen sink: The use of multiple hypothesis generation methods to investigate an outbreak of Salmonella Enteritidis associated with frozen profiteroles and eclairs.

In December 2018, an outbreak of Salmonella Enteritidis infections was identified in Canada by whole-genome sequencing (WGS). An investigation was initiated to identify the source of the illnesses, which proved challenging and complex. Microbiological hypothesis generation methods included comparisons of Salmonella isolate sequence data to historical domestic outbreaks and international repositories. Epidemiological hypothesis generation methods included routine case interviews, open-ended centralized re-interviewing, thematic analysis of open-ended interview data, collection of purchase records, a grocery store site visit, analytic comparison to healthy control groups, and case-case analyses. Food safety hypothesis testing methods included food sample collection and analysis, and traceback investigations. Overall, 83 cases were identified across seven provinces, with onset dates from 6 November 2018 to 7 May 2019. Case ages ranged from 1 to 88 years; 60% (50/83) were female; 39% (22/56) were hospitalized; and three deaths were reported. Brand X profiteroles and eclairs imported from Thailand were identified as the source of the outbreak, and eggs from an unregistered facility were hypothesized as the likely cause of contamination. This study aims to describe the outbreak investigation and highlight the multiple hypothesis generation methods that were employed to identify the source.

A multi-provincial outbreak of Salmonella Newport infections associated with red onions: A report of the largest Salmonella outbreak in Canada in over 20 years.

An investigation into an outbreak of Salmonella Newport infections in Canada was initiated in July 2020. Cases were identified across several provinces through whole-genome sequencing (WGS). Exposure data were gathered through case interviews. Traceback investigations were conducted using receipts, invoices, import documentation, and menus. A total of 515 cases were identified in seven provinces, related by 0-6 whole-genome multi-locus sequence typing (wgMLST) allele differences. The median age of cases was 40 (range 1-100), 54% were female, 19% were hospitalized, and three deaths were reported. Forty-eight location-specific case sub-clusters were identified in restaurants, grocery stores, and congregate living facilities. Of the 414 cases with exposure information available, 71% (295) had reported eating onions the week prior to becoming ill, and 80% of those cases who reported eating onions, reported red onion specifically. The traceback investigation identified red onions from Grower A in California, USA, as the likely source of the outbreak, and the first of many food recall warnings was issued on 30 July 2020. Salmonella was not detected in any tested food or environmental samples. This paper summarizes the collaborative efforts undertaken to investigate and control the largest Salmonella outbreak in Canada in over 20 years.

Fermenting a place in history: The first outbreak of Escherichia coli O157 associated with kimchi in Canada.

A Canadian outbreak investigation was initiated in January 2022 after a cluster of cases of Shiga-toxin-producing Escherichia coli (STEC) O157 was identified through whole genome sequencing (WGS). Exposure information was collected through case interviews. Traceback investigations were conducted, and samples from case homes, retail, and the manufacturer were tested for STEC O157. Fourteen cases were identified in two provinces in Western Canada, with isolates related by 0-5 whole genome multi-locus sequence typing allele differences. Symptom onset dates ranged from 11 December 2021 to 7 January 2022. The median age of cases was 29.5 (range 0-61); 64% were female. No hospitalisations or deaths were reported. Of 11 cases with information available on fermented vegetable exposures, 91% (10/11) reported consuming Kimchi Brand A during their exposure period. The traceback investigation identified Manufacturer A in Western Canada as the producer. One open and one closed sample of Kimchi Brand A tested positive for STEC O157, with isolates considered genetically related by WGS to the outbreak strain. Napa cabbage within the kimchi product was hypothesised as the most likely source of contamination. This paper summarises the investigation into this STEC O157 outbreak associated with kimchi, the first reported outside of East Asia.

Outbreak of Vibrio parahaemolyticus Associated with Consumption of Raw Oysters in Canada, 2015.

There has been a steady increase in illness incidence of Vibrio parahaemolyticus (Vp). The majority of illnesses are associated with consumption of raw oysters. In the summer of 2015, Canada experienced the largest outbreak associated with the consumption of raw oysters harvested from British Columbia (BC) coastal waters. Case investigation of laboratory-confirmed cases was conducted to collect information on exposures and to assist traceback. Investigations at processors and oyster sampling were conducted. Eighty-two laboratory-confirmed cases of Vp infection were reported between January 1 and October 26, 2015. The majority of the cases were reported in BC, associated with consumption of raw BC oysters in restaurants. Sea surface temperatures were above the historical levels in 2015. This outbreak identified the need to improve surveillance and response to increases in human cases of Vp. This is of particular importance due to the potential for increasing water temperatures and the likelihood of additional outbreaks of Vibrio.

Escherichia coli O157:H7 Infections Associated with Contaminated Pork Products - Alberta, Canada, July-October 2014.

During July-October 2014, an outbreak of 119 Escherichia coli O157:H7 infections in Alberta, Canada was identified through notifiable disease surveillance and investigated by local, provincial, and federal public health and food regulatory agencies. Twenty-three (19%) patients were hospitalized, six of whom developed hemolytic uremic syndrome; no deaths were reported. Informed by case interviews, seven potential food sources were identified and investigated. The majority of patients reported having consumed meals containing pork at Asian-style restaurants in multiple geographically diverse Alberta cities during their exposure period. Traceback investigations revealed a complex pork production and distribution chain entirely within Alberta. E. coli O157:H7-contaminated pork and pork production environments and mishandling of pork products were identified at all key points in the chain, including slaughter, processor, retail, and restaurant facilities. An outbreak-specific pulsed-field gel electrophoresis (PFGE) cluster pattern was found in clinical and pork E. coli O157:H7 isolates. Measures to mitigate the risk for exposure and illness included pork product recalls, destruction of pork products, temporary food facility closures, targeted interventions to mitigate improper pork-handling practices identified at implicated food facilities, and prosecution of a food facility operator. Pork should be considered a potential source in E. coli O157:H7 investigations and prevention messaging, and pork handling and cooking practices should be carefully assessed during regulatory food facility inspections.

Influence of School Year on Seasonality of Norovirus Outbreaks in Developed Countries.

Factors affecting the seasonal distribution of norovirus outbreaks are not well understood. This study examined whether grade school settings at the start of the school year may be a factor. We searched Ovid Medline from January 2002 to June 2014 for studies that provided all reported norovirus outbreaks in a developed country by month for a minimum of three years. Historical school years were obtained from verifiable sources. The start of the norovirus seasonal outbreak peak and peak outbreak month were determined for each study and compared to the start month of school. Northern hemisphere and southern hemisphere countries had a different norovirus seasonality and different school year structures (traditional compared to year round). In the two studies that provided outbreaks by age, outbreaks among children started several months before outbreaks in the adult population. The median number of months between school start and start of the seasonal outbreak peak was two months (interquartile range [IQR] = 2.0-3.0), while the median number of months between school start and peak outbreak month was four months (IQR = 3.0-4.0). These findings suggest the possibility the school setting at the start of the school year may be a factor in the seasonality of norovirus.

The utility of multiple molecular methods including whole genome sequencing as tools to differentiate Escherichia coli O157:H7 outbreaks.

A standardised method for determining Escherichia coli O157:H7 strain relatedness using whole genome sequencing or virulence gene profiling is not yet established. We sought to assess the capacity of either high-throughput polymerase chain reaction (PCR) of 49 virulence genes, core-genome single nt variants (SNVs) or k-mer clustering to discriminate between outbreak-associated and sporadic E. coli O157:H7 isolates. Three outbreaks and multiple sporadic isolates from the province of Alberta, Canada were included in the study. Two of the outbreaks occurred concurrently in 2014 and one occurred in 2012. Pulsed-field gel electrophoresis (PFGE) and multilocus variable-number tandem repeat analysis (MLVA) were employed as comparator typing methods. The virulence gene profiles of isolates from the 2012 and 2014 Alberta outbreak events and contemporary sporadic isolates were mostly identical; therefore the set of virulence genes chosen in this study were not discriminatory enough to distinguish between outbreak clusters. Concordant with PFGE and MLVA results, core genome SNV and k-mer phylogenies clustered isolates from the 2012 and 2014 outbreaks as distinct events. k-mer phylogenies demonstrated increased discriminatory power compared with core SNV phylogenies. Prior to the widespread implementation of whole genome sequencing for routine public health use, issues surrounding cost, technical expertise, software standardisation, and data sharing/comparisons must be addressed.

Emergence of a new norovirus GII.4 variant and changes in the historical biennial pattern of norovirus outbreak activity in Alberta, Canada, from 2008 to 2013.

The public health impact of the emergence of new norovirus (NoV) strains is uncertain. A biennial pattern of alternating quiescent and epidemic levels of NoV outbreak activity associated with the emergence of new GII.4 variants was observed in Alberta, Canada, between July 2000 and June 2008. In this study, NoV genogroup I (GI) and GII strains isolated from 710 outbreak specimens in Alberta between July 2008 and January 2013 were characterized to update historical data. The seasonality and annual variation in NoV outbreak burden were analyzed over a 10-year period (July 2002 to June 2012). We found that GII.4-2006b had persisted as the predominant variant over three observation periods (July 2006 to June 2009) during which the biennial NoV outbreak pattern continued. The emergence of GII.4-2010 (winter 2009) was not associated with increased outbreak activity, and outbreak activity between July 2009 and June 2012 when GII.4-2010 predominated (67.5 to 97.7%) did not follow a biennial pattern. GII.4-2012 first emerged in Alberta in September 2011 and became predominant in observation period July 2012 to June 2013. NoV GI, relatively rare in past years, had a higher activity level (37.3%) as represented by GI.6 and GI.7 in the winter of 2012 to 2013. A higher proportion of GI outbreaks occurred in non-health care facility settings compared to GII. Our study suggests that factors other than new variants emergence contribute to the levels of NoV outbreak activity in Alberta.

A multi-function public health surveillance system and the lessons learned in its development: the Alberta Real Time Syndromic Surveillance Net.

OBJECTIVE: We describe a centralized automated multi-function detection and reporting system for public health surveillance--the Alberta Real Time Syndromic Surveillance Net (ARTSSN). This improves upon traditional paper-based systems which are often fragmented, limited by incomplete data collection and inadequate analytical capacity, and incapable of providing timely information for public health action. METHODS: ARTSSN concurrently analyzes multiple electronic data sources in real time to describe results in tables, charts and maps. Detected anomalies are immediately disseminated via alerts to decision-makers for action. RESULTS: ARTSSN provides richly integrated information on a variety of health conditions for early detection of and prompt action on abnormal events such as clusters, outbreaks and trends. Examples of such health conditions include chronic and communicable disease, injury and environment-mediated adverse incidents. DISCUSSION: Key advantages of ARTSSN over traditional paper-based methods are its timeliness, comprehensiveness and automation. Public health surveillance of communicable disease, injury, environmental hazard exposure and chronic disease now occurs in a single system in real time year round. Examples are given to demonstrate the public health value of this system, particularly during Pandemic (H1N1) 2009.

Outbreak of Escherichia coli O157:H7 Infections Linked to Mechanically Tenderized Beef and the Largest Beef Recall in Canada, 2012.

Contaminated beef is a known vehicle of Escherichia coli O157:H7 infection, although more attention is given to the control of E. coli O157:H7 in ground, rather than whole-cut, beef products. In September 2012, an investigation was initiated at an Alberta, Canada, beef plant after the detection of E. coli O157:H7 in two samples of trim cut from beef originating from this plant. Later in September 2012, Alberta Health Services identified five laboratory-confirmed infections of E. coli O157:H7, and case patients reported eating needle-tenderized beef steaks purchased at a store in Edmonton, Alberta, produced with beef from the Alberta plant. In total, 18 laboratory-confirmed illnesses in Canada in September and October 2012 were linked to beef from the Alberta plant, including the five individuals who ate needle-tenderized steaks purchased at the Edmonton store. A unique strain of E. coli O157:H7, defined by molecular subtyping and whole genome sequencing, was detected in clinical isolates, four samples of leftover beef from case patient homes, and eight samples of Alberta plant beef tested by industry and food safety partners. Investigators identified several deficiencies in the control of E. coli O157:H7 at the plant; in particular, the evaluation of, and response to, the detection of E. coli O157 in beef samples during routine testing were inadequate. To control the outbreak, 4,000 tons of beef products were recalled, making it the largest beef recall in Canadian history. This outbreak, in combination with similar outbreaks in the United States and research demonstrating that mechanical tenderization can transfer foodborne pathogens present on the surface into the interior of beef cuts, prompted amendments to Canada's Food and Drug Regulations requiring mechanically tenderized beef to be labeled as such and to provide safe cooking instructions to consumers. A detailed review of this event also led to recommendations and action to improve the safety of Canada's beef supply.

Modifiable risk factors for invasive meningococcal disease during an Edmonton, Alberta outbreak, 1999-2002.

BACKGROUND: An outbreak of invasive meningococcal disease (IMD) in metro Edmonton, Alberta, Canada between December 1999 and June 2002 resulted in 84 laboratory-confirmed cases. Most cases were infected with Neisseria meningitidis serogroup C, and the highest age-specific incidence was observed in the 15-19 year age group. METHODS: A case-control study was conducted to identify modifiable IMD risk factors among outbreak cases. Two controls were matched to each case on age and sex, and were recruited through random-digit dialing. A questionnaire was telephone-administered to 132 study participants (44 cases, 88 controls). Conditional logistic regression was utilized to calculate risk measures. RESULTS: Multivariate analysis revealed three statistically significant risk factors: bar patronage (OR 35.2; 95% CI: 2.64-468), "rave" attendance (OR 12.8; 95% CI: 1.47-111) and maternal smoking (OR 8.88; 95% CI: 1.67-47.4). Humidifier use in the home was protective (OR 0.07; 95% CI: 0.009-0.64). CONCLUSION: While the precision of risk estimates was low in the multivariate model, this study has identified rave attendance as an emergent IMD risk factor.

Outbreak of Escherichia coli O157:H7 Infections Linked to Aged Raw Milk Gouda Cheese, Canada, 2013.

Between 12 July and 29 September 2013, 29 individuals in five Canadian provinces became ill following infection with the same strain of Escherichia coli O157:H7 as defined by molecular typing results. Five case patients were hospitalized, and one died. Twenty-six case patients (90%) reported eating Gouda cheese originating from a dairy plant in British Columbia. All of the 22 case patients with sufficient product details available reported consuming Gouda cheese made with raw milk; this cheese had been produced between March and July 2013 and was aged for a minimum of 60 days. The outbreak strain was isolated from the implicated Gouda cheese, including one core sample obtained from an intact cheese wheel 83 days after production. The findings indicate that raw milk was the primary source of the E. coli O157:H7, which persisted through production and the minimum 60-day aging period. This outbreak is the third caused by E. coli O157:H7 traced to Gouda cheese made with raw milk in North America. These findings provide further evidence that a 60-day ripening period cannot ensure die-off of pathogens that might be present in raw milk Gouda cheese after production and have triggered an evaluation of processing conditions, physicochemical parameters, and options to mitigate the risk of E. coli O157:H7 infection associated with raw milk Gouda cheese produced in Canada.

Clinical, microbiological, and epidemiological findings of an outbreak of Mycobacterium abscessus hand-and-foot disease.

In 2003, we identified an outbreak of clinically distinct lesions involving the hands and feet associated with a public wading pool in Edmonton, Alberta, Canada. A total of 85 cases were identified. The management and follow-up of 41 children and 1 adult patients is presented. Skin lesions occurred within a median incubation period of 29 days and approximately 88 days for the adult patient. Lesions resolved within a median of 58 days and approximately 150 days for the adult patient. Patients were treated with clarithromycin, topical antibiotic dressings, and/or incision and drainage of pustules or followed without treatment. All resolved without complication. The pool was closed and cleaned. The M. abscessus hand-and-foot disease is characterized by the onset, mainly in children, of tender, erythematous papules, pustules, and abscesses with a self-limited course. This is the first documented M. abscessus outbreak associated with wading pool exposure.

An outbreak of E. coli O157:H7 hemorrhagic colitis associated with unpasteurized gouda cheese.

BACKGROUND: A cluster of E. coli O157:H7 hemorrhagic colitis was identified in metro Edmonton, Alberta through notifiable disease surveillance in late 2002. METHODS: Environmental health officers collected food histories and clinical information from cases in the cluster. The provincial public health laboratory conducted pulsed field gel electrophoresis (PFGE) analysis on E. coli O157:H7 isolates from cluster cases. Public health and food regulatory agencies conducted an investigation when a food source (unpasteurized gouda cheese) was implicated. RESULTS: PFGE analysis revealed an "outbreak" profile in 13 cases. Onset dates for the outbreak cases ranged between October 2002 and February 2003. Two cases, aged 22 months and 4 years, developed hemolytic uremic syndrome as a result of their infection. Consumption of unpasteurized gouda cheese produced at a local dairy farm was reported by 12 of 13 outbreak cases in the 2 to 8 days prior to illness. E. coli O157:H7 was isolated from 2 of 26 cheese samples manufactured by the implicated producer. The cheese isolates had indistinguishable PFGE profiles as compared with outbreak case isolates. Implicated cheese was found to be contaminated with E. coli O157:H7 104 days after production, despite having met regulated microbiological and aging requirements. CONCLUSION: To our knowledge, this is the first confirmed outbreak of E. coli O157:H7 infection in Canada associated with raw milk hard cheese. A review of federal legislation vis-à-vis raw milk hard cheese may be in order.

Myiasis in an urban setting: A case report.

Myiasis is considered to be a condition only found in tropical, developing countries. However, this paper reports a case identified in an urban, North American setting. The clinical presentation is discussed along with the underlying comorbidities and social determinants.

Histoplasmosis cluster, golf course, Canada.

We report a cluster of 4 cases of acute histoplasmosis (1 culture proven and 3 with positive serology, of which 2 were symptomatic) associated with exposure to soil during a golf course renovation. Patients in western Canada with compatible symptoms should be tested for histoplasmosis, regardless of their travel or exposure history.

Was it something she ate? Case report and discussion of scombroid poisoning.

We report the case of a 51-year old woman who developed headache, nausea, palpitations, tachycardia and hypertension 30 minutes after eating a tuna fish salad. Elevated histamine levels in the salad helped to confirm a suspected diagnosis of scombroid poisoning. The signs, symptoms, pathophysiology and management of poisoning from spoiled scombroid fish are discussed.