Shigellosis is more severe than other forms of gastroenteritis. This is because when Shigella bacteria multiply in the human gut they invade cells and result in much tissue destruction.7 Also, many strains produce a toxin called “shiga toxin” which is very potent and destructive. Shiga toxin is very similar to the verotoxin of E. coli O157:H7.
Shigellosis usually resolves in 5 to 7 days, although it may be several months before a victim’s bowel habits are entirely normal. In some persons, especially young children, the elderly, and immune compromised persons, the diarrhea can be so severe that the patient needs to be hospitalized. The hospitalization rate for shigellosis is estimated to be in excess of 50,000 per year in the United States.8 Complications of shigellosis include severe dehydration, seizures in small children, rectal bleeding, and invasion of the blood stream by the bacterium.

More than one million deaths occur in the developing world yearly due to infections with Shigella. The victims are mostly children.7 In the United States, it is estimated that about 700 persons die yearly from shigellosis.8 Small children and the elderly are at greatest risk to experience mortality from a Shigella infection.
Up to 3% of persons who are infected with Shigella may later develop a syndrome that includes joint pain and swelling, irritation of the eyes, and sometimes painful urination as well. This is a reaction to the previous gastroenteritis and is called ìreactive arthritis.î It is also called Reiter’s Syndrome. It occurs because of protein mimicry; basically, the immune system, intending to fight Shigella, attacks the self.9 Reiter’s Syndrome is most common in persons with the HLA-B27 genetic makeup. (Testing for this is readily available.) Reiter’s Syndrome can last for months or years, can lead to chronic arthritis, and may be difficult to treat.