In the fall of 2011, staff from federal, state, and local health and agriculture agencies investigated an outbreak of E. coli O157:H7 infections associated with pre-packaged romaine lettuce. Fourteen states reported 26 outbreak associated cases. Five people were hospitalized. No one died.

Routine surveillance interviews with 8 cases identified early in the outbreak revealed that all 8 cases reported consuming Brand A pre-packaged salad; multiple varieties were reported. Romaine lettuce was the only ingredient common to the Brand A pre-packaged lettuce varieties reported by the cases. A traceback investigation was conducted by the Minnesota Department of Agriculture, the Illinois Department of Agriculture, the Wisconsin Department of Agriculture and the FDA. Romaine lettuce from 9 lots and five growers were found to be in common across the four traceback legs. Additional information by FDA from the Brand A Franklin Park, Illinois facility indicated that two lots of romaine lettuce from two growers in the Salinas Valley, California could have provided the implicated lettuce. An environmental assessment at Farm A indicated that romaine lettuce was irrigated with water from an open reservoir next to a cattle ranch, suggesting a possible source of contamination. However, this was not confirmed.