Due to the fact that the organisms live in the intestines of healthy cattle, preventive measures on cattle farms and during meat processing are being investigated. E-Coli O157:H7 is one of hundreds of strains of the bacterium Escherichia coli. Although most strains are harmless and live in the intestines of healthy humans and animals, this strain produces a powerful toxin and can cause severe illness. E-Coli O157:H7 was first recognized as a cause of illness in 1982 during an outbreak of severe bloody diarrhea; the outbreak was traced to contaminated hamburgers. Since then, most infections have come from eating undercooked ground beef.
Hemorrhagic colitis, the first E-Coli symptom, is characterized by the sudden onset of abdominal pain and severe cramps, followed within 24 hours by diarrhea. As the disease progresses, the diarrhea becomes watery and then may become bloody. E-Coli symptoms sometimes include vomiting and fever. The incubation period for E-Coli infection (i.e., the period from ingestion of the bacteria to the start of symptoms) is typically 3 to 9 days, although shorter and longer periods are not that unusual. An incubation period of less than 24 hours would be unusual. In most infected individuals, the E-Coli symptoms last about a week and resolve without any long term problems.