After an outbreak of Yersinia in Sweden, imported iceberg lettuce has ended up as the suspected source of infection. From January until the beginning of February this year, twice as many people fell ill with Yersinia infection as did during the same period in a normal year.
From 53 cases of Yersinia enterocolitica, 33 lived in Stockholm, Västra Götaland and Halland. Isolates from 24 of these cases were typed by whole genome sequencing and 16 outbreak patients with clustered isolates of sequence type 18 could be identified.
According to Rikard Dryselius, microbiologist at Folkhälsomyndigheten (Public Health Agency of Sweden), collection and typing of Yersinia isolates is not done routinely in the country: “Instead, individual counties can ask for help with typing Yersinia when they see a need. Alternatively, we may ask the laboratories to send in isolates if we see an increase in cases nationally that should be investigated.”
Folkhälsomyndigheten, infection control units in the Stockholm, Västra Götaland and Halland regions and Livsmedelsverket (Swedish Food Agency) investigated the incident.
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