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

Thomas Inns*, Paul Cleary, Nick Bundle, Sarah Foulkes, Ashley Sharp, Lara Utsi, Chris McBrien, Rehman Teagle, Alison Waldram, Chris Williams, Cathy McCann, Rob Smith, Sepeedeh Saleh, Noel McCarthy, Roberto Vivancos, Jeremy Hawker, Valerie Decraene

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

There is a need for innovative methods to investigate outbreaks of food-borne infection linked to produce with a complex distribution network. The investigation of a large outbreak of Escherichia coli O157 PT34 infection in the United Kingdom in 2016 indicated that catering venues associated with multiple cases had used salad leaves sourced from one supplier. Our aim was to investigate whether catering venues linked to cases were more likely to have used salad leaves from this supplier. We conducted a matched case-control study, with catering venues as the units of analysis. We compared venues linked to cases to those without known linked cases. We included 43 study pairs and obtained information on salad leaf products received by each venue. The odds of a case venue being supplied with salad leaves by Supplier A were 7.67 times (95% confidence interval: 2.30-25.53) those of control venues. This association provided statistical evidence to support the findings of the other epidemiological investigations undertaken for this outbreak. This is a novel approach which is labour-intensive but which addresses the challenge of investigating exposures to food across a complex distribution network.

Original languageEnglish
Article number17-00195
JournalEurosurveillance
Volume23
Issue number18
DOIs
Publication statusPublished - 3 May 2018

Bibliographical note

Funding Information:
This paper is written on behalf of the Outbreak Control Team Epidemiology Cell; we would like to acknowledge the contribution of all members. We would particularly like to thank all the Environmental Health Officers involved for the time and effort they spent obtaining the food chain information used in this study. Thomas Inns, Paul Cleary, Noel McCarthy, Roberto Vivancos and Jeremy Hawker are affiliated to the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Gastrointestinal Infections at University of Liverpool in partnership with Public Health England (PHE), in collaboration with University of East Anglia, University of Oxford and the Quadram Institute. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, the Department of Health or Public Health England.

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