Necrotizing fasciitis, commonly known as flesh-eating bacteria, is a rare but aggressive opportunistic bacterial disease in the Streptococcus family. Like other opportunistic diseases, such as Staphylococcus, it usually enters through a break in the skin. However, unlike staph, fasciitis spreads very quickly, particularly in the cells just below the skin, the fascia (from which it draws it name), causing complications such as gangrene in the affected area. It spreads more slowly through the bloodstream, but spreads quickly through affected tissue. Although it doesn't actually "eat" tissue, it does release toxins that damage tissue often causing death within days of initial symptoms, usually from the side effects of the dying tissue poisoning the body.
Fasciitis rarely affects healthy people and tends to occur in the immunocompromised, diabetics, alcoholics and systemic diseases. It generally presents initially with intense pain with no sign of trauma, or minimal trauma and no initial symptoms on the skin. The delay in skin symptoms depends on where the infection starts - the deeper the initial infection, the longer it takes for it to appear on the skin. If untreated, death is usually by toxic shock.
Fasciitis can be treated with powerful narrow spectrum antibiotics, but once the disease has progressed, antibiotics will usually not slow the progression of the disease enough to prevent the death of the patient. In such cases, amputation of the affected parts is usually the only effective treatment.
One of the most famous victims of the disease is Lucien Bouchard, the former premiere of the province of Quebec in Canada, who lost a leg to the disease.
In the episode Three Stories, the farmer patient was exposed to the bacteria through a dog bite. Remarkably, the bacteria can exist in a dog's mouth without infecting the dog.