How is E. coli O157:H7 spread?

The organism can be found on most cattle farms, and it is commonly found in petting zoos and can live in the intestines of healthy cattle, deer, goats, and sheep. Meat can become contaminated during slaughter, and organisms can be accidentally mixed into meat when it is ground. Bacteria present on the cow's udders or on equipment may get into raw milk. In a petting zoo, E.coli O157:H7 can contaminate the ground, railings, feed bins, and fur of the animals.

Eating meat, especially ground beef, that has not been cooked sufficiently to kill E. coli O157:H7 can cause infection. Contaminated meat looks and smells normal. The number of organisms required to cause disease is very small.

Among other known sources of infection are consumption of sprouts, lettuce, spinach, salami, unpasteurized milk and juice, and by swimming in or drinking sewage-contaminated water.

Bacteria in loose stool of infected persons can be passed from one person to another if hygiene or hand washing habits are inadequate. This is particularly likely among toddlers who are not toilet trained. Family members and playmates of these children are at high risk of becoming infected.

Young children typically shed the organism in their feces for a week or two after their illness resolves. Older children and adults rarely carry the organism without symptoms.

Date: September 24, 2006
Content source: Coordinating Center for Infectious Diseases / Division of Bacterial and Mycotic Diseases