Escherichia coli O157:H7 was first recognized as a pathogen in 1982 during an outbreak investigation of hemorrhagic colitis (1). E. coli O157 infection can lead to hemolytic uremic syndrome (HUS), characterized by hemolytic anemia, thrombocytopenia, and renal injury (2). Still, it was not until 1993, after a large multistate E. coli O157 outbreak linked to undercooked ground beef patties sold from a fast-food restaurant chain (3), that E. coli O157 became broadly recognized as an important and threatening pathogen. Clinical laboratories began examining more stool specimens for E. coli O157 (4). In 1994, E. coli O157 became a nationally notifiable infection, and by 2000, reporting was mandatory in 48 states. An estimated 73,480 illnesses due to E. coli O157 infection occur each year in the United States, leading to an estimated 2,168 hospitalizations and 61 deaths annually (5), and it is an important cause of acute renal failure in children (6,7).
