A bacterium that lives harmlessly in the intestines of animals such as cattle, reptiles, and birds. However, in humans the bacterium, which can be transmitted by foods, animal contact, and drinking water, can cause bloody diarrhea, and also lead to hemolytic uremic syndrome (HUS), a life threatening disease. Although other generic strains of E. coli are thought to be harmless to humans, the O157:H7 strain is particularly virulent and dangerous. USDA began an E. coli O157:H7 testing plan in 1994. As part of the Hazard Analysis and Critical Control Point (HACCP) rule,all meat and poultry slaughter plants are required to test carcasses regularly for generic E. coli in order to verify that their sanitary systems are effectively controlling fecal contamination.