This was the first reported multistate outbreak of E. coli O157:H7 infections associated with the consumption of lettuce. At first cases were identified in Connecticut and Illinois. Separate case control studies implicated the consumption of mesclun lettuce as a risk factor for illness. The mesclun lettuce had been purchased from multiple retail outlets, suggesting a central point of contamination. Traceback of the implicated lettuce led to a single company. Lettuce was found to be growing next to cattle pastures. Well water supplied the cattle and provided crop irrigation. Unclean water was used to process the lettuce. There were no handwashing facilities for field staff. The lettuce had been shipped to five states, California, Florida, Connecticut, Illinois, and New York. California and Florida did not identify any cases matching the outbreak strain, however New York subsequently found sixteen cases that matched the outbreak strain.