The Middleton outbreak: 125 cases of foodborne salmonellosis resulting from cross-contaminated food items served at a picnic and a smorgasbord.

One hundred and twenty-five of 173 people who ate at a picnic and/or a smorgasbord prepared by a bar-restaurant in a Midwestern town in September 1973 developed diarrhea, abdominal cramps, and other symptoms 23 hours (median time) later. Eleven were hospitalized. Stool cultures from 18 ill individuals grew Salmonella infantis, Salmonella agona, and Salmonella schwarzengrund. Stool cultures from 5 of 8 restaurant employees grew S. infantis or S. agona. Cultures of remaining foods and food-contact surfaces were negative. Food-specific attack rates, based on interviews with 121 eaters, implicated potato salad and chicken dressing as vehicles of transmission, both likely contaminated when prepared in pans that shortly before contained uncooked, chicken pieces suspected to have harbored salmonellae. Chickens were eventually traced to 3 farms where feed samples were found to contain Salmonella typhimurium and Salmonella cubana, raising the possibility that other feed samples may have contained the serotypes responsible for the outbreak. The main control measure was temporarily closing the food service, which was to have catered a large church picnic the next day. The outbreak had an economic impact estimated at $28,733.