Yersinia enterocolitica: A Follow-up of the Outbreak in the Norwegian Armed Forces in 2014
Authors: Borud Einar Kristian , Håberg Siri Eldevik , Norheim Arne Johan , Strand Leif Åge , Fadum Elin Anita 
Published: December 2020

ABSTRACT

Introduction
In the spring of 2014, there was an outbreak of Yersinia enterocolitica (YE) gastroenteritis in four Norwegian military camps—the largest outbreak ever reported in Norway. YE is usually transmitted via food, and the gastrointestinal disease caused by the bacterium is considered a public health problem in several countries. Common symptoms of YE gastroenteritis are abdominal pain, diarrhea, fever, nausea, and vomiting. Post-infectious complications can occur after YE gastroenteritis, the most common of which are erythema nodosum and reactive arthritis. Based on self-reported data, we describe the duration of illness, the duration of any absence from service, and the incidence of symptoms of post-infectious complications in two groups of servicepeople: one diagnosed with YE gastroenteritis and the other with an unspecified acute infectious gastroenteritis.

Materials and Methods
The Norwegian Armed Forces Health Register (NAFHR) is a central health register that contains data from conscripts and from military and civilian personnel in the Norwegian Armed Forces. In this study, we identified all individuals with a diagnosis of YE gastroenteritis in the NAFHR in the period from January 1 to June 30, 2014 (n = 128) as well as all those with a diagnosis of an unspecified acute infectious gastroenteritis in the same period (n = 323) to participate as controls. In October 2018, a link to an internet-based questionnaire was distributed by e-mail to all identified individuals. The questionnaires collected data on the duration of illness, the duration of absence from service, and the incidence of symptoms of post-infectious complications.

Results
Of all those who received the questionnaire, 72 (59%) were included in the YE group and 117 people (36%) were included in the control group. Half of those in the YE group were ill for more than 13 days, while almost all (90%) of those in the control group recovered after 1 week. There were no differences between the groups in the incidence of symptoms of post-infectious complications during the 6 weeks after recovery. There was a significantly larger proportion of officers than conscripts in the YE group who reported symptoms of post-infectious complications. None of the respondents reported symptoms of post-infectious complications in the 6 months after the termination of military service.

Conclusion
One strength of this study is that we were able to investigate a large outbreak of YE gastroenteritis in a group of individuals with good underlying health. Weaknesses are the low response rate, especially in the control group, and the fact that we sent out the questionnaire &gt;4 years after the acute gastroenteritis occurred. YE gastroenteritis among personnel in the Norwegian Armed Forces was associated with a significantly longer duration of illness and a longer duration of absence from service than that resulting from an unspecified acute infectious gastroenteritis. However, YE gastroenteritis was not associated with more symptoms of post-infectious complications.