Shigella infection (shigellosis) is an intestinal infection caused by a family of bacteria known as shigella. The main sign of shigella infection is diarrhea, which often is bloody.
Shigella is very contagious. People get infected with shigella when they come in contact with and swallow small amounts of bacteria from the stool of a person who is infected with shigella. For example, this can happen in a child care setting when staff members don't wash their hands well enough after changing diapers or helping toddlers with toilet training. Shigella bacteria can also be passed in infected food or by drinking or swimming in unsafe water.
Children under age 5 are most likely to get shigella infection, but it can occur at any age. A mild case usually clears up on its own within a week. When treatment is needed, doctors generally prescribe antibiotics.
Signs and symptoms of shigella infection usually begin a day or two after contact with shigella. But it may take up to a week to develop. Signs and symptoms may include:
- Diarrhea (often containing blood or mucus)
- Stomach pain or cramps
- Nausea or vomiting
Symptoms generally last for about five to seven days. In some cases, symptoms may last longer. Some people have no symptoms after they've been infected with shigella. However, their feces may still be contagious up to a few weeks.
When to see a doctor
Contact your doctor or seek urgent care if you or your child has bloody diarrhea or diarrhea severe enough to cause weight loss and dehydration. Also, contact your doctor if you or your child has diarrhea and a fever of 101 F (38 C) or higher.
Infection occurs when you accidentally swallow shigella bacteria. This can happen when you:
- Touch your mouth. Direct person-to-person contact is the most common way the disease is spread. For example, if you don't wash your hands well after changing the diaper of a child who has shigella infection, you may become infected yourself.
- Eat contaminated food. Infected people who handle food can spread the bacteria to people who eat the food. Food can also become infected with shigella bacteria if it grows in a field that contains sewage.
- Swallow contaminated water. Water may become infected with shigella bacteria either from sewage or from a person with shigella infection swimming in it.
- Being a child. Children under age 5 are most likely to get shigella infection. But shigella can infect people of any age.
- Living in group housing or participating in group 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.
- Living or traveling in areas that lack sanitation. People who live or travel in developing countries are more likely to get shigella infection.
- Being a man who has sex with men. Men who have sex with men are at higher risk of shigella infection because of direct or indirect oral-anal contact during sexual activity.
Shigella infection usually clears up without complications. But it may take weeks or months before your bowel habits return to normal.
Complications may include:
- Dehydration. Constant diarrhea can cause dehydration. Signs and 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 with a shigella infection have seizures. Seizures are more common in children who run a high fever, but can occur in children who do not have a high fever. It's not known whether the seizures 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 or inflammation of the large intestine 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 a type of E. coli bacteria than by shigella bacteria, 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 stomach 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).
- Bloodstream infections (bacteremia). Shigella infection can damage the lining of the intestines. In rare cases, shigella bacteria can enter the bloodstream through the damaged intestinal lining and cause a bloodstream infection.
Although researchers continue to work to develop a shigella vaccine, nothing is available yet. To prevent the spread of shigella:
- Wash hands with soap and water for at least 20 seconds frequently
- Watch small children when they wash their hands
- Throw away soiled diapers properly
- Disinfect diaper-changing areas after use
- Don't prepare food for others if you have diarrhea
- Keep children with diarrhea home from child care, play groups or school
- Avoid swallowing water from ponds, lakes or untreated pools
- Avoid sexual activity with anyone who has diarrhea or who recently recovered from diarrhea
- Don't go swimming until you have fully recovered.