The California Department of Public Health (CDPH) detected an outbreak of six cases of E. coli O157:H7 and reported these to the Food Safety and Inspection Service (FSIS) in July, 2010. The E. coli O157:H7 that was identified was an unusual strain as determined by pulsed field gel electrophoresis (PFGE) subtyping, a genetic fingerprinting technique. Subsequently a seventh case was discovered that had occurred earlier, in February. Eating hamburger patties produced by Valley Meats Company, produced at the Modesto, California, plant apparently was determined to be a risk factor for illness. On August 6, approximately 1000000 pounds of frozen ground beef patties and bulk ground beef products were recalled by the company. The meat had been distributed to food service providers in California, Texas, Arizona, and internationally.