A delicatessen's potato salad was tested Tuesday as the possible source of one of the nation's largest known E. coli outbreaks, with as many as 4,500 people sickened.
Meanwhile in Georgia, a virulent form of E. coli traced to a water park sickened at least six children.
The Illinois outbreak, which occurred the weekend of June 6, struck customers at Iwan's Deli and Catering in southwest suburban Orland Park.
An estimated 4,000 to 4,500 people became ill as a result of the bacterium enterotoxigenic escherichia coli.
A statistical analysis showed that potato salad could have caused the problem, but there would be no certainty until after results of tests are available, said Sean McDermott, a spokesman for the Cook County Department of Public Health.
Dr. Paul Mead of the federal Centers for Disease Control and Prevention said the outbreak was the largest documented in the U.S. of the relatively rare bacterium.