RESEARCH ARTICLE Risk Factors for Sporadic Domestically Acquired Campylobacter Infections in Norway 2010–2011: A National Prospective Case-Control Study

Background Campylobacteriosis is the most frequently reported food- and waterborne infection in Nor-way. We investigated the risk factors for sporadic Campylobacter infections in Norway in order to identify areas where control and prevention measures could be improved. Methods A national prospective case-control study of factors associated with Campylobacter infec-tion was conducted from July 2010 to September 2011. Cases were recruited from the Nor-wegian Surveillance System of Communicable Diseases (MSIS). Controls were randomly selected from the Norwegian Population Registry. Cases and controls were mailed a paper questionnaire with a prepaid return envelope. Univariable analyses using logistic regression were conducted for all exposures. A final parsimonious multivariable model was developed using regularized/penalized logistic regression, and adjusted odds ratios were calculated. Results A total of 995 cases and 1501 controls were included in the study (response proportion 55