One of the primary causes of foodborne illness is Escherichia coli (E. coli) O157:H7. While most strains of E. coli are harmless, this particular one can cause severe illness. The vast majority of cases are not fatal but the CDC (Center for Disease Control and Prevention) estimates that the illness affects 73,000 persons a year. The most common causes of infection are eating undercooked meat, drinking raw milk, or exposing oneself to contaminated water. It is often present in and on animals, and therefore farms and petting zoos are common sites of contamination. Once infected, poor hygiene can lead to its spread from person to person. Symptoms, including diarrhea, bloody diarrhea, and stomach cramps, typically occur within two and eight days of exposure and it rarely takes longer than 10 days for the ill individual to recover.

E. coli O157:H7 can be diagnosed by testing the stool. In fact, all bloody stool should be tested for E. coli. Treatment is usually unnecessary; most recover without any care or medication. Antibiotics should not be used, as no benefit has been demonstrated with regard to E. coli and they can have many unintended side-effects.

Infection with E. coli O157:H7 is diagnosed by detecting the bacterium in the stool. All diarrhea with blood should get their stool tested for E. coli O157:H7. In increasingly rare instances, there can be long-term side effects, such as blindness, paralysis, and persistent kidney failure.

There are many steps which can be taken to prevent the spread of E.coli. These include thoroughly cooking all meat, particularly ground beef. This is best done with a thermometer. It is advisable, when eating out, to not eat burgers that are still pink on the inside. Rather, they should be sent back to be cooked further and one should ask for a new bun and plate as well. In the kitchen, raw meat should be handled with care, always separated from ready to eat food, and hands washed after contact. To further avoid the risk of infection, one should only drink milk, juice, or cider that has been pasteurized. This means that it has been heated to destroy the presence of any pathogens, such as E. coli.

Fruits and vegetables should be thoroughly washed before eating; those particularly concerned should only each cooked vegetables and fruits that have been peeled. Finally, those in contact with diarrhea (whether because they themselves are ill or because they are changing diapers, etc) should thoroughly wash their hands with hot water and soap. Those with diarrheal illnesses should avoid actions that might spread the disease, such as swimming in public pools or lakes, sharing bathes, or involvement in the preparation of food.