title: [An outbreak of Yersinia enterocolitica O:9-infection].
abstract: BACKGROUND
  Yersiniosis is a zoonosis that is transmitted from pigs to humans. In January 2006 more cases of Yersinia enterocolitica enterocolitis than expected were reported in Norway. The fact that the isolates belonged to the O:9 serogroup, which is rare in Norway, and the geographical and temporal clustering of the cases, pointed to an outbreak. We have conducted a retrospective study of 11 patients who were diagnosed during this outbreak.
  
  
  METHODS
  The material is based upon applicants' information, patient journals and a questionnaire. In order to disclose the source of infection, a case-control survey was performed.
  
  
  RESULTS
  Nine of the 11 patients had enterocolitis and two had septicaemia, both of whom died following a few days of treatment. One patient presented with pseudo- appendicitis while another developed monoarthritis, which persisted for more than three months after the debut of symptoms Treatment with antibiotics was offered in six cases. The case-control analysis indicated that brawn was the probable source of infection.
  
  
  CONCLUSIONS
  This is the first reported Norwegian outbreak of Y. enterocolitica O:9 disease. The incubation time, disease duration and frequency of intestinal and immunological complications corresponds with previously published data. The frequency of septicaemia exceeds several previously reported outbreaks and retrospective studies of sporadic cases.
authors.affiliation: Mikrobiologisk laboratorium Sykehuset i Vestfold Postboks 2168 Postterminalen 3103 Tønsberg. tore.stenstad@siv.no.
authors.forename: Tore
authors.initials: T
authors.lastname: Stenstad
authors.forename: Danica
authors.initials: D
authors.lastname: Grahek-Ogden
authors.forename: Marit
authors.initials: M
authors.lastname: Nilsen
authors.forename: Dagfinn
authors.initials: D
authors.lastname: Skaare
authors.forename: Tore-Arne
authors.initials: TA
authors.lastname: Martinsen
authors.forename: Jørgen
authors.initials: J
authors.lastname: Lassen
authors.forename: Anne-Lise
authors.initials: AL
authors.lastname: Bruu
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D016022:Case-Control Studies; D004196:Disease Outbreaks; D005260:Female; D005516:Food Microbiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D012189:Retrospective Studies; D018805:Sepsis / Q000382:microbiology; D012703:Serotyping; D011795:Surveys and Questionnaires; D013552:Swine; D015009:Yersinia Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000209:etiology; D015008:Yersinia enterocolitica / Q000145:classification / Q000302:isolation & purification