Investigation of &i&Yersinia enterocolitica&/i& Bioserotype 4/O:3 Clusters in Finland, 2017-2018

摘要

In December 2017, two suspected outbreaks of Yersinia enterocolitica 4/O:3 were notified in Finland. We analyzed the surveillance and outbreak investigation data and genotyped Y. enterocolitica strains in order to understand Y. enterocolitica epidemiology in Finland and to find out whether the notified outbreaks were related. A total of 13,344 Y. enterocolitica cases were reported in 1995-2018 to the National Infectious Diseases Register. The mean annual incidence ranged from 7.9 to 15.9/100,000 inhabitants. The highest incidence was observed in young adults (14/100,000). Incidence varied geographically. The incidence was higher in spring compared to other seasons. The most common pathogenic bioserotype was 4/O:3 but the information on bio/serotype was missing in 64% of the surveillance cases. For most of the cases, 87%, no travel history was reported. In the YE 4/O:3 outbreak investigation, whole genome sequencing was performed for isolates from 29/69 (42%) of the outbreak cases. The sequencing results showed that cases consisted of six independent clusters with 2 - 6 isolates in each cluster, and 5 sporadic isolates. No food item was found to be common to all of the clusters. In order to improve monitoring and facilitate the detection and investigation of Y. enterocolitica outbreaks, more comprehensive information on bio/serotype and on travel history is required in the surveillance.