In September 2005, a large number of E. coli O157:H7 infections in King and Pierce Counties in Washington revealed contaminated parsley used at an Olive Garden restaurant.

Later that same month, more infections surfaced, from parsley used at three other Olive Garden restaurants and The Boat Shed restaurant.

In October, more than 20 customers at McGrath’s Fish House also reported incidents of E. coli poisoning. Parsley was again determined to be the source of the outbreak.

Investigators initiated a trace-back of produce suppliers to determine which supplier provided the parsley to the restaurants. The investigation lead to a single grower in Oregon. The Washington Department of Health as well as the Oregon Department of Agriculture were notified.