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Updated: Aug 15, 2026

A High-throughput Platform for the Screening of Salmonella spp./Shigella spp.
Published on: November 7, 2018
Use of sequential case-control studies to investigate a community Salmonella outbreak in Wales
L J Llewellyn1, M R Evans, S R Palmer
1Public Health Laboratory Service Communicable Disease Surveillance Centre (Welsh Unit), Cardiff.
Study Objective:
To establish the source of a community outbreak of Salmonella typhimurium definitive type 124.
Design:
Two stage case-control study.
Setting:
Three districts in south east Wales.
Subjects:
Cases of salmonella food poisoning and community controls.
Main Results:
An initial case-control study identified an association between illness and eating ham (odds ratio 4.50, 95% confidence intervals 1.10, 21.8) and also found a possible association between illness and food bought from delicatessen stores (odds ratio 5.03, 95% confidence intervals 1.01, 32.3). However, only after a second stage case-control study was a single common ham producer identified as the source (odds ratio 25.0, 95% confidence intervals 2.33, 1155).
Conclusion:
Sequential case-control studies are an important and underused tool in the investigation of community outbreaks.
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