Novel application of the matched case-control design to compare food supply chains during an Escherichia coli O157 outbreak, United Kingdom, 2016

Gastrointestinal symptoms and the acquisition of enteric pathogens in Hajj pilgrims: a 3-year prospective cohort study

The acquisition of enteric pathogens and risk factors for Hajj-associated diarrhea in Hajj pilgrims is poorly documented. Pilgrims from Marseille participating in the Hajj in 2016-2018 underwent successive systematic rectal swabbing before and after their travel. Carriage of the main enteric pathogens was assessed by real-time PCR. Baseline demographics, adherence to individual preventive measures, gastrointestinal symptoms, and treatments were recorded. A total of 376 pilgrims were included. The median age was 62.0 years. During the Hajj, 18.6% presented at least one gastrointestinal symptom, 13.8% had diarrhea, and 36.4% had acquired at least one enteric pathogen. Enteropathogenic Escherichia coli (EPEC) and Enteroaggregative E. coli (EAEC) were the pathogens most frequently acquired by pilgrims (17.6% and 14.4%, respectively). Being female was associated with increased frequency of gastrointestinal symptoms during the pilgrimage (aOR = 2.38, p = 0.004). Enterohemorrhagic Escherichia coli (EHEC) acquisition was associated with a four-fold higher risk of reporting at least one gastrointestinal symptom and diarrhea (aOR = 3.68 and p = 0.01 and aOR = 3.96 and p = 0.01, respectively). Pilgrims who suffered from diarrhea were more likely to wash their hands more often (aOR = 2.07, p = 0.03) and to be either overweight (aOR = 2.71, p = 0.03) or obese (aOR = 2.51, p = 0.05). Enteric bacteria such as E. coli that are frequently associated with traveler's diarrhea due to the consumption of contaminated food and drink were frequently found in pilgrims. Respecting strict measures regarding food and water quality during the Hajj and adherence to preventive measures such as good personal hygiene and environmental management will help reduce the burden of gastrointestinal infections at the event.

Use of an ingredient-based analysis to investigate a national outbreak of Escherichia coli O157, United Kingdom, July 2016

Public Health England was alerted to a national outbreak of Shiga toxin-producing Escherichia coli O157 PT34 in July 2016. Early investigations suggested that the likely source was a salad item consumed outside of the home. A number of cases reported consuming meals at a staff canteen (Venue A) and a garden café (Venue B). Both venues shared a common salad supplier. An investigation was undertaken to measure associations between salad items and illness using an 'ingredient-based analysis'. A retrospective case-control study was conducted using an online questionnaire to collect information on menu items consumed at each venue. Chefs at both venues were interviewed to identify ingredients contained within each menu item. Both venues were pooled together for multivariable analysis measuring associations at the ingredient level. Among 203 responses, 24 cases were identified (13 confirmed, two probable and nine possible). Case onsets ranged between 7 and 25 June 2016. Multivariable analysis identified strong evidence that only baby mixed-leaf salad from the common supplier was a vehicle of infection (adjusted odds ratio = 13.1; 95% confidence interval: 1.6-106.5). Identifying the specific salad ingredient associated with illness was made possible by using an ingredient-based analysis. We recommend the increased use of ingredient-based analyses.