A BEACH-ASSOCIATED OUTBREAK OF ESCHERICHIA-COLI O157-H7

On July 5, 1995, the Winnebago County Health Department in northern Il linois reported a cluster of five Escherichia coli O157:H7 cases in ch ildren. Interviews with the children's parents revealed no common food or drinking-water source, but all the children had visited Rock Cut S tate Park, which contains a bathing beach, on June 24 or June 25, 1995 . The beach was closed on July 6, 1995, because of suspected transmiss ion of infection through lake water. An initial case control study con firmed that the outbreak was associated with swimming at the beach. A second case control study determined that taking lake water into the m outh, swallowing lake water, and time spent in the water were all risk factors for illness. An environmental investigation of the facility a nd the watershed, including drinking-water and beach-water analyses, r evealed no likely source for the outbreak. The outbreak ultimately inc luded 12 cases and was attributed to fecal discharge from a swimmer or swimmers.