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.