Do Differences in Risk Factors, Medical Care Seeking, or Medical Practices Explain the Geographic Variation in Campylobacteriosis in Foodborne Diseases Active Surveillance Network (FoodNet) Sites?

Background. In the United States, considerable geographic variation in the rates of culture-confirmed Campylobacter infection has been consistently observed among sites participating in the Foodborne Diseases Active Surveillance Network (FoodNet). Methods. We used data from the FoodNet Population Surveys and a FoodNet case-control study of sporadic infection to examine whether differences in medical care seeking, medical practices, or risk factors contributed to geographic variation in incidence. Results. We found differences across the FoodNet sites in the proportion of persons seeking medical care for an acute campylobacteriosis-like illness (range, 24.9%-43.5%) and in the proportion of ill persons who submitted a stool sample (range, 18.6%-40.7%), but these differences were not statistically significant. We found no evidence of geographic effect modification of previously identified risk factors for campylobacteriosis in the case-control study analysis. The prevalence of some exposures varied among control subjects in the FoodNet sites, including the proportion of controls reporting eating chicken at a commercial eating establishment (18.2%-46.1%); contact with animal stool (8.9%-30.9%); drinking water from a lake, river, or stream (0%-5.1%); and contact with a farm animal (2.1%-12.7%). However, these differences do not fully explain the geographic variation in campylobacteriosis. Conclusions. Future studies that quantify Campylobacter contamination in poultry or variation in host immunity may be useful in identifying sources of this geographic variation in incidence.