A multistate outbreak (Cluster ID # 0906WIEXH-1) of E. coli O157:H7 was detected linked to ground beef produced by the JBS Swift Company. Most ill persons had consumed ground beef; many reported that it was undercooked. Samples from unopened packages of ground beef recovered from a patient's home were tested by the Michigan Public Health Laboratory. These yielded E. coli O157:H7 that matched the "DNA fingerprint" of the outbreak strain. Twenty three persons had been infected with the strain that matched by standard DNA testing. The beef was sold in the United States and Mexico. Mexican health officials banned further importation of the meat.