Each hamburger can contain meat and, potentially bacteria, from hundreds of animals. The US outbreak that catapulted this organism to national prominence occurred at a fast-food chain serving hamburgers that were not thoroughly cooked. Much is now known about this infection. There have been outbreaks throughout the world. It was first recognized as an enteric pathogen in 1982.
Healthy cattle harbor the organism and are the major reservoir.
In addition to undercooked ground beef, outbreaks have been caused by ingestion of well water, apple cider, mayonnaise, raw milk, fresh fruits and vegetables, lettuce and alfalfa sprouts and by swimming in ponds or other unchlorinated water. The organism can survive fermentation and drying. A low infectious dose is required for disease, and it can be shed from stool for weeks after symptoms resolve. Person to person transmission is common. It causes a spectrum of disease from mild, non-bloody diarrhea to hemorrhagic colitis.