Shiga-toxigenic Escherichia coli O157:H7 infections among livestock exhibitors and visitors at a Texas County Fair.

We report an agricultural fair-associated shiga-toxigenic Escherichia coli O157:H7 (STEC O157) outbreak that was unusual in that it affected both livestock exhibitors and visitors. Twenty-five human cases of STEC O157 infection were detected after the Fort Bend County Fair in Rosenberg, Texas, which ran from 9/26/03 to 10/04/03. Seven cases were culture-confirmed. There were four hemolytic uremic syndrome (HUS) cases, and one thrombotic thrombocytopenic purpura (TTP) case. Cases ranged in age from 18 months to 67 years. Twenty-two (88%) cases were female. Analysis of unmatched case-control data linked STEC O157 infection with visiting fair livestock exhibit areas and with multiple fair visits. All outbreak-related isolates were of a single STEC O157 subtype. Fair Ground environmental sampling and culture for STEC O157, conducted 46 days after the end of the Fair, yielded multiple STEC O157 isolates, including the outbreak subtype. Livestock exhibitors and fair visitors should follow guidelines to reduce the risk of transmission of STEC O157 at agricultural fairs.