Campylobacter is the most common bacterial cause of diarrheal illness. In 2012, the Foodborne Diseases Active Surveillance Network (FoodNet) estimated the incidence to be 14.3 cases per 100,000 population. An estimated 1.3 million persons are affected each year.

An estimated 2 million cases of Campylobacter enteritis occur annually in the U.S., accounting for 5-7% of cases of gastroenteritis. A large animal reservoir is present, with up to 100% of poultry, including chickens, turkeys, and waterfowl, having asymptomatic infections in their intestinal tracts. An infected chicken may contain up to 10⁹ bacteria per 25 grams, and due to the installations, the bacteria is rapidly spread to other chicken. Ten to five hundred bacteria are enough to infect humans. Campylobacter enteritis has a classical seasonal pattern characterized by a peak incidence in early summer, and then a steady decline in winter.