Outbreak of Shigella sonnei Infection Linked to Iceberg Lettuce
Author Information
Author(s): J.A. Frost, M.B. McEvoy, C.A. Bentley, Y. Andersson, B. Rowe
Primary Institution: Central Public Health Laboratory, London, England
Hypothesis
Is iceberg lettuce associated with sporadic Shigella sonnei infection in adults?
Conclusion
The study found strong evidence that consumption of iceberg lettuce was linked to Shigella sonnei infections.
Supporting Evidence
- Of 100 reported cases of Sh. sonnei infection in Sweden, 52 occurred in two outbreaks in mid-May.
- 38 out of 40 case patients had eaten iceberg lettuce.
- Illness was significantly associated with iceberg lettuce consumption (relative risk 3.68).
- 27 cases and 44 controls were analyzed in the study.
Takeaway
Eating iceberg lettuce might make you sick with a type of bacteria called Shigella. This study looked at people who got sick and found a lot of them had eaten lettuce.
Methodology
A case-control study was conducted where cases were matched with controls based on age, sex, and area of residence.
Potential Biases
Potential bias from self-selection of case patients and reliance on recall for food consumption.
Limitations
The source of the iceberg lettuce could not be traced, and the study relied on self-reported food consumption.
Participant Demographics
Median age of case-patients was 47 years, with a range of 19 to 79 years; 19 were women and 8 were men.
Statistical Information
P-Value
0.0172
Confidence Interval
1.26 to 150.5
Statistical Significance
p = 0.0172
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