On July 8, 2002, the U.S. Centers for Disease Control and Prevention (CDC) was notified by the Colorado Department of Public Health and Environment (CDPHE) of a cluster of cases of Escherichia coli O157:H7 infection. CDPHE has identified 20 cases of E. coli O157 infection, with onset dates between June 13 and 30, and isolates that are indistinguishable when tested by pulsed field gel electrophoresis (PFGE) using two enzymes. Based on patient interviews, molecular fingerprinting methods, and initial traceback, these cases have been associated with consumption of ground beef products voluntarily recalled by ConAgra Beef Company on June 30, 2002.

Using PulseNet and epidemiologic information, 14 additional cases of E. coli O157 infection that might be related to the Colorado cluster have been identified. Sick persons include residents of nine other states including Alabama, California, Iowa, Michigan, Nebraska, Ohio, South Dakota, Washington, and Wyoming.

Of these 34 cases, 10 persons have been hospitalized, six have hemolytic uremic syndrome, and one person has died.

PulseNet, CDC's National Molecular Subtyping Network for Foodborne Disease Surveillance consists of a network of public health laboratories that perform a DNA "fingerprinting" method called pulsed-field gel electrophoresis (PFGE) on foodborne bacteria. The network permits rapid comparison of these fingerprint patterns through an electronic database.