Signs and symptoms of shigella infection usually begin a day or two after contact with shigella, but may take up to a week to develop. Signs and symptoms may include:

• Diarrhea (often containing blood or mucus)
• Abdominal pain or cramps
• Fever

Although some people have no symptoms after they've been infected with shigella, their feces may still be contagious up to a few weeks.

Infection occurs when you accidentally swallow shigella bacteria. This can happen when you:

• Touch your mouth. If you don't wash your hands well after changing the diaper of a child who has shigella infection, you may become infected yourself. Direct person-to-person contact is the most common way the disease is spread.
• Eat contaminated food. Infected people who handle food can transmit the bacteria to people who eat the food. Food can also become contaminated if it grows in a field that contains sewage.
• Swallow contaminated water. Water may become contaminated either from sewage or from a person with shigella infection swimming in it.

• Age. Children under age 5 are most likely to get shigella infection, but it can occur at any age.
• Living arrangements and activities. Close contact with other people spreads the bacteria from person to person. Shigella outbreaks are more common in child care centers, community wading pools, nursing homes, jails and military barracks.
• Time spent in areas that lack sanitation. People who live or travel in developing countries are more likely to contract shigella infection.
• Men who have sex with men. Men who have sex with men are at higher risk because of direct or indirect oral-anal contact.

Shigella infection usually clears up without complications, although it may take weeks or months before your bowel habits return to normal.

Complications may include:

• Dehydration. Persistent diarrhea can cause dehydration. Symptoms include lightheadedness, dizziness, lack of tears in children, sunken eyes and dry diapers. Severe dehydration can lead to shock and death.
• Seizures. Some children who run high fevers with a shigella infection have seizures. It's not known whether the convulsions are a result of the fever or the shigella infection itself. If your child has a seizure, contact your doctor immediately.
• Rectal prolapse. In this condition, straining during bowel movements may cause the mucous membrane or lining of the rectum to move out through the anus.
• Hemolytic uremic syndrome. This rare complication of shigella, more commonly caused by bacteria called E. coli, can lead to a low red blood cell count (hemolytic anemia), low platelet count (thrombocytopenia) and acute kidney failure.
• Toxic megacolon. This rare complication occurs when your colon becomes paralyzed, preventing you from having a bowel movement or passing gas. Signs and symptoms include abdominal pain and swelling, fever, and weakness. If you don't receive treatment for toxic megacolon, your colon may break open (rupture), causing peritonitis, a life-threatening infection requiring emergency surgery.
• Reactive arthritis. Reactive arthritis develops in response to an infection. Signs and symptoms include joint pain and inflammation, usually in the ankles, knees, feet and hips; redness, itching and discharge in one or both eyes (conjunctivitis); and painful urination (urethritis).