LAUSR

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 >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.