The Swedish Public Health Agency says the outbreak of Yersinia enterocolitica is over.
During the period January and up to the beginning of February, twice as many people fell ill with Yersinia infection as during the same period in a normal year. Of a total of 53 cases of Yersinia enterocolitica, 33 were resident in the regions of Stockholm, Västra Götaland and Halland.
Isolates from 24 of these cases were typed by whole genome sequencing, ie analysis of the bacterium’s genome, and 16 outbreak cases with clustered isolates could be identified.
The Swedish Public Health Agency and the infection control units have collaborated on interviews with sick people and compilation of questionnaire responses about what and where they ate before the illness. A so-called case-case study where questionnaire responses from outbreak cases were compared with questionnaire responses from disease cases with Yersinia infection that did not belong to the outbreak, it emerged that the outbreak cases had to a greater extent visited one and the same restaurant chain.
A contaminated batch of iceberg lettuce distributed to a restaurant chain is the suspected source of infection.
