The U.S. military base in Okinawa, Japan, treated three cases of E. coli O157:H7 in February. The joint investigation by U.S. and Japanese authorities ensued as these three cases were Japanese citizens. Two of the cases had purchased ground beef patties from the military commissary in Okinawa prior to their illnesses. E. coli O157:H7 was isolated from consumer samples of frozen, hamburger patties. Commissary samples of hamburger patties of the same lot number were also tested to eliminate the possibility of contamination after opening. These samples showed the presence of E. coli O157:H7. The E. coli O157:H7 isolated from the ground beef and the people were of the same genetic pattern. This pattern had not previously been observed in Japan and was not in the PulseNet database. A traceback through the U.S. Department of Agriculture found that the distributor of the contaminated beef had also sent ground beef patties to other U.S. military installations in the Far East and to non-military retailers in California, Idaho, Oregon and Washington. This investigation resulted in the recall of 90,000 pounds of frozen ground beef and other ground beef products. Later an additional related case was found in a military family in Japan; two additional cases were found in a non-military family in California.