The UK Outbreak Control Team
Publication date: September 2011
Report of the findings of the investigation of an outbreak of foodborne Salmonella Bareilly infection in the UK in 2010. Between August and mid December 2010 (weeks 30 to 50), 220 laboratory confirmed outbreak cases of S. Bareilly infection (excluding travel related cases and infections with non outbreak strains of S. Bareilly) were identified across England, Wales, and Northern Ireland. An additional 21 cases were identified in Scotland, bringing the UK total to 241 cases.
Epidemiological and microbiological investigations implicated bean sprouts as a vehicle for S. Bareilly transmission, consistent with previous outbreak investigations that identified bean sprouts as a vehicle for Salmonella transmission. A case control study showed that consumption of bean sprouts was significantly associated with being a case (odds ratio 6.8, 95% confidence interval 1.4 to 33.0). S. Bareilly with an indistinguishable pulsed field gel electrophoresis (PFGE) pattern from outbreak cases was also detected in a number of samples of commercially produced bean sprouts.
As in previous outbreaks, this investigation concluded that the seeds were likely to have been contaminated at source prior to importation. The investigation found that the method used for routine microbiological quality control testing of bean sprouts might not be sensitive to low levels of Salmonella contamination. This may have implications for future testing protocols.
Public health interventions resulting from this investigation focused mainly on communications to the general public and to environmental health professionals advising on the correct preparation of bean sprouts, and on improving information on food labels where this was ambiguous. The investigation concluded that raising public awareness to ensure the correct preparation of raw bean sprouts during cooking was the principal means of minimising risk to consumers and reducing further cases.
The outbreak was declared over on 21 January 2011, when reports of cases of S. Bareilly had fallen to background levels.
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Last reviewed: 16 December 2011