Later that month, the WDOH was notified that two more persons were hospitalized with bloody diarrhea and presumed to have E. coli O157:H7. Laboratory testing would soon confirm infection with E. coli O157:H7 and PFGE analysis linked the infection to the four earlier E. coli cases. Environmental inspections and food histories identified salad ingredients parsley, served with each person’s entree, as possible sources of E. coli.
Later, additional Washington residents with laboratory confirmed E. coli O157:H7 were determined to be part of the cluster. Seven of the eight individuals identified in the outbreak had eaten fresh parsley served in three separate restaurants.
Health officials in Oregon, aware of the outbreak in Washington State, noticed an increase in E. coli O157:H7 cases in mid-October of 2005. More than 20 persons who lived in the Bend, Oregon area were reporting diarrhea. The Deschutes Health Department investigated and found that all of the ill individuals had eaten at a restaurant with a common parsley supplier to the Washington restaurants associated with the E. coli outbreak. A case-control study also implicated parsley served in food or as a garnish as the source of E. coli among the Oregon E. coli outbreak victims.