Shigellosis

What Is It?

Shigellosis is an infection of the colon (large intestine) caused by Shigella bacteria. Shigellosis sometimes is called bacillary dysentery because it can cause severe diarrhea. However, the infection often causes only mild symptoms.

Shigella can be found in water polluted with infected sewage, and they commonly enter the body through a contaminated drinking supply. Shigella bacteria also can be found on food that has been rinsed with unclean water, grown in fields contaminated with sewage, or touched by flies that have touched feces. Especially among children, Shigella bacteria can be carried to the mouth on dirty fingers that have touched items soiled with feces, including dirty diapers, toilets and bathroom fixtures. Outbreaks of shigellosis are most common in areas where sanitation is poor, and in places where people live under confined or crowded conditions. Shigella also can be passed from person to person during anal-oral sex.

Worldwide, an estimated 140 million people develop shigellosis each year, and about 600,000 die. Most of these deaths occur in developing countries among children under age 5. In the United States, only 20,000 cases are reported each year, but the actual number of infections is probably more than 200,000 per year. Shigella is more common among children ages 1 to 4. Children of this age are especially at risk of shigellosis because they are starting to use the toilet and often forget the basics of good hygiene. Infants are at the highest risk of becoming seriously ill from a Shigella infection.

Symptoms

Although health experts do not know why, some people are able to take in Shigella bacteria without becoming ill. Others develop only a brief fever, or a brief fever together with mild diarrhea that goes away on its own. About 25% of patients, however, develop high fever, abdominal cramping and severe diarrhea that can contain blood, mucus and pus. These patients can have 10 to 30 bowel movements each day, together with a persistent urge to have a bowel movement that can lead to rectal prolapse (an abnormal protrusion of the rectum). Rarely, Shigella bacteria can affect other parts of the body that are far from the digestive tract. When this happens, there can be seizures, confusion or coma, kidney failure, arthritis, rashes or other symptoms.