http://www.cdc.gov/mmwr/preview/mmwrhtml/00042070.htm

On July 5, 1995, the Winnebago County Health Department (WCHD) in northern Illinois received a report from the local hospital of five cases of Escherichia coli O157:H7 infection among children who resided in Rockford. Interviews of the children's parents revealed no common food source; however, on June 24-25, they all had visited an Illinois state park with a lake swimming beach. WCHD and IDPH investigated the outbreak to assess risk factors for illness and determine the source of infection. This report summarizes the findings of the investigation, which indicate that ingesting contaminated and untreated lake water can result in infection. It presents bibliographic references.