Outbreak of Salmonella Newport linked to imported frozen cooked crayfish in dill brine, Sweden, July to November 2019

In autumn 2019, the Public Health Agency of Sweden identified a cluster of Newport cases by whole genome sequencing (WGS). Cases' distribution in place and time indicated a nation-wide ongoing outbreak. An investigation was initiated to identify the source and prevent further cases. We conducte...

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Bibliographic Details
Published in:Euro surveillance : bulletin européen sur les maladies transmissibles 2022-06, Vol.27 (22), p.1
Main Authors: Jansson Mörk, Marie, Karamehmedovic, Nadja, Hansen, Anette, Nederby Öhd, Joanna, Lindblad, Mats, Östlund, Emma, Rehn, Moa, Jernberg, Cecilia
Format: Article
Language:English
Subjects:
Anethum graveolens
Animals
Astacoidea
Bacterial infections
Brine
Disease Outbreaks
Disease transmission
Epidemics
Fish
Food contamination & poisoning
Humans
Medicin och hälsovetenskap
Outbreaks
Salmonella
Salmonella - genetics
Salts
Sweden - epidemiology
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Summary:In autumn 2019, the Public Health Agency of Sweden identified a cluster of Newport cases by whole genome sequencing (WGS). Cases' distribution in place and time indicated a nation-wide ongoing outbreak. An investigation was initiated to identify the source and prevent further cases. We conducted a case-case study based on notified salmonellosis cases and a trawling questionnaire, comparing 20 outbreak cases and 139 control cases. Food exposures were compared by adjusted odds ratios (aOR) with 95% confidence interval (CI) using logistic regression. Implicated foods were sampled. Outbreak cases were more likely to have consumed crayfish (aOR = 26; 95% CI: 6.3-105). One specific brand of imported frozen, pre-cooked whole crayfish in dill brine was identified as the source. Newport was later detected in different batches from retail and in one sample from border control. Isolates from food samples clustered with the human outbreak strain by WGS. Although the retailer made a complete recall, two more cases were identified long afterwards. This investigation demonstrated the successful use of a case-case study and targeted microbiological testing to identify the source. The immediate action taken by the retailer was important to confirm the source and stop the outbreak.
ISSN:1560-7917
1025-496X
1560-7917
DOI:10.2807/1560-7917.ES.2022.27.22.2100918