On September 12, 2005 Public Health Seattle King County received an unusual number of E. coli O157:H7 reports. Case interviews by county investigators subsequently revealed that three unrelated residents of King County and one Pierce County resident had all eaten at the same Olive Garden restaurant in Federal Way on September 1, 2005 and had all become ill on September 5; two were hospitalized. Investigators determined that all four individuals had eaten the house salad and fresh parsley used either as a topping or as an ingredient in entrees.
Pulsed field gel electrophoresis (PFGE) analysis of the bacterium isolated from patients’ stool samples was conducted at the Washington Department of Health (WDOH) Public Health Laboratory. Results showed that all four patients were infected with a genetically indistinguishable strain of E. coli O157:H7.
On September 29, 2005, WDOH received a report that two Kitsap County residents had been hospitalized with E. coli O157:H7 infections. Both had eaten at The Boat Shed restaurant on September 10 and had consumed salad ingredients and parsley, which was served with each person’s entree. Laboratory testing and PFGE analysis linked the strain of E. coli to the strain isolated from the four Olive Garden cases reported in mid-September.
Public health officials learned that two additional Washington residents with laboratory-confirmed E. coli O157:H7 were part of the cluster. Those case-patients were from Clark and Whatcom Counties. Seven of the eight individuals identified as part of the outbreak had eaten fresh parsley served in three separate restaurants.
WDOH environmental health staff conducted a trace-back of produce suppliers to the three restaurants where exposure to E. coli O157:H7 had occurred and learned that parsley was the only item that had been supplied by a single grower from Oregon. On October 12 the Food and Drug Administration (FDA) was notified of the outbreak and contacted the Food Safety Division at the Oregon Department of Agriculture (ODA), which joined the investigation.
Health officials in Oregon, aware of the outbreak in Washington State, noticed an increase in E. coli O157:H7 cases in mid-October. More than 20 Bend, Oregon-area residents had become ill after eating at McGrath’s Fish House between October 12 and October 14, 2005. Two of the individuals had submitted stool specimens which cultured positive for the same strain of E. coli O157:H7 as that isolated from the Washington case-patients.
A case-control study implicated parsley served in food or as a garnish as the source of E. coli O157:H7 among McGrath’s Restaurants patrons. Furthermore, Oregon health investigators traced the source of the parsley served at McGrath’s to the same farm that supplied parsley to the Olive Garden and The Boat Shed.
Marler Clark represented a Washington resident in a claim against the parsley supplier. The claim was resolved in 2006.