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

Shiga toxin-producing Escherichia coli, such as E. coli O157 have the potential to cause severe gastrointestinal disease, with infection leading to haemolytic uraemic syndrome (HUS) in 5–14% of cases [1]. The incidence of E. coli O157 has increased in England and Wales since 2005; incidence is highest in children younger than 10 years [2]. There have been a number of large E. coli O157 outbreaks in the United Kingdom (UK) [3,4], several linked to contaminated foods with wide distribution networks [5-7]. Food traceback investigations can be important for determining the source of E. coli outbreaks caused by contaminated food items [8-10]