Shigella infection

Shigella infection (shigellosis) is an intestinal disease caused by a family of bacteria called shigella. The main sign of shigella infection is diarrhea, which often is bloody.

Shigella can be acquired through direct contact with the bacteria in the stool, such as in a child care setting when staff members don’t wash their hands adequately after changing diapers. Shigella bacteria also can be passed in contaminated food or by drinking or swimming in contaminated water.

Children between ages 2 and 4 are most likely to get shigellosis. Shigella infection is far more common in developing nations, especially where there’s overcrowding and poor sanitation.

If you’re in good health, a mild case of shigellosis is likely to clear up on its own. When shigella infection requires treatment, doctors generally prescribe antibiotics.

Symptoms of shigellosis

Signs and symptoms of shigellosis usually begin a day or two after exposure to shigella. Signs and symptoms may include:

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


Different types of shigella bacteria cause shigellosis. Subgroup D shigella (Shigella sonnei) causes more than two-thirds of shigellosis in the United States, with subgroup B (Shigella flexneri) accounting for most of the rest. The bacteria penetrate the lining of your intestine, causing swelling and possibly causing sores to develop.

Poor hygiene and inadequate hand washing can cause shigella to spread from an infected person. Toddlers in the process of toilet training may contract shigellosis, and then pass it to family members and playmates.

Eating contaminated food can cause shigellosis. Food that looks and smells normal may become contaminated as a result of:

  • Handling by an infected person who fails to wash adequately after using the toilet
  • Growing in a field that contains sewage
  • Coming into contact with flies that breed in infected feces

Drinking water infected with shigella or swimming in infected water can cause shigellosis as well. Water may become contaminated either from sewage or from a person with shigella infection swimming in it.

In developing nations, some types of the shigella germ can cause deadly epidemics.

Shigella infection is highly contagious, particularly for children. Spending time in a child care setting or a long term care facility, especially where staff or others don’t wash their hands adequately, can put you at risk.

Severe diarrhea in a young child, older adult or someone with a chronic illness can lead to severe dehydration, which can cause shock and death. Symptoms of dehydration may include lightheadedness, dizziness, lack of tears in children, sunken eyes and dry diapers.

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 accompanied by a fever of 101 F (38 C) or higher. With a shigella infection, a fever can run as high as 106 F (41 C).


Diarrhea and bloody diarrhea can result from a number of diseases. Confirming shigellosis involves taking a sample of your stool to be tested in a laboratory for the presence of shigella bacteria.


Shigella infection usually clears up without complications, although it may take weeks or months before your bowel habits return to normal. However, severe, untreated dehydration can lead to shock and death. Chronically ill adults and children younger than 2 are at greatest risk.

Children are at greatest risk of other shigella infection complications, which may include:

  • 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. Most seizures are brief, but if your child has one that lasts longer than five minutes or is accompanied by vomiting, problems with breathing or extreme sleepiness, get emergency medical attention immediately.
  • Proctitis. The bacteria that cause shigellosis may also cause inflammation of the lining of the rectum.
  • Rectal prolapse. In this condition, straining during bowel movements may cause the rectal mucous membrane, or lining, to move down or through the anus.
  • Hemolytic uremic syndrome. This rare complication of shigella, more commonly caused by bacteria called Escherichia coli (E. coli) O157:H7, can lead to a low red blood cell count (hemolytic anemia), low platelet count (thrombocytopenia) and acute kidney failure.

Other complications may include:

  • 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. You might also become disoriented or groggy. If you don’t receive treatment for toxic megacolon, your colon may rupture, causing peritonitis, a life-threatening condition requiring emergency surgery.
  • Reiter syndrome. If you get shigellosis from subgroup B shigella, you may be at risk of Reiter syndrome, but only if you have a genetic predisposition. Reiter syndrome is a form of reactive arthritis, which develops in response to infection. Signs and symptoms of Reiter syndrome include joint pain and inflammation, usually in the ankles, knees, feet and hips. Symptoms may also include redness, itching and discharge in one or both eyes (conjunctivitis), and painful urination (urethritis).


Shigella infection usually runs its course in five to seven days. Replacing lost fluids from diarrhea may be all the treatment you need, particularly if your general health is good and your shigella infection is mild. Other treatments may be necessary in more-severe cases.

Treatments include:

  • Antibiotics. For severe shigella infection, which may last for weeks, antibiotics may shorten the duration of the illness. However, some shigella bacteria, particularly those contracted in developing nations, have become drug resistant. So it’s better not to take antibiotics unless your shigella infection is severe, in which case your doctor may prescribe an antibiotic such as sulfamethoxazole with trimethoprim (Bactrim, Septra, others), azithromycin (Zithromax, Zmax) or ciprofloxacin (Cipro). Antibiotics may also be necessary for infants, older adults and people who have HIV infection, as well as in situations where there’s high risk of spreading the disease.
  • Fluid and salt replacement. For generally healthy adults, drinking water may be enough to counteract the dehydrating effects of diarrhea. Children may benefit from an oral rehydrating solution, such as Pedialyte, available in drugstores. These solutions contain water and salts in specific proportions to replenish both fluids and electrolytes — minerals such as sodium, potassium and calcium that maintain the balance of fluids in your body.

Children and adults who are severely dehydrated need treatment in a hospital emergency room, where they can receive electrolytes and fluids through a vein (intravenously), rather than by mouth. Intravenous hydration provides the body with water and essential nutrients much more quickly than oral solutions do.

Don’t take anti-diarrheal agents
Drugs intended to treat diarrhea, such as loperamide (Imodium) and diphenoxylate with atropine (Lomotil), can make your condition worse. Don’t take them.


Hand washing
Good hygiene, particularly thorough and frequent hand washing, is the best way to prevent the spread of shigella infection. Follow these instructions:

  • Wet your hands with warm, running water and apply liquid or clean bar soap. Lather well.
  • Rub your hands vigorously together for at least 15 seconds.
  • Scrub all surfaces, including the backs of your hands, wrists, between your fingers and under your fingernails.
  • Rinse well.
  • Dry your hands with a clean or disposable towel.
  • Use a towel to turn off the faucet.

It’s especially important to wash your hands after using the toilet or changing diapers and before preparing food. If soap and water aren’t available, use an alcohol-based hand sanitizer. Commercially prepared hand sanitizers contain ingredients that help prevent skin dryness, so they may be less drying than soap and water and may kill germs better. Be sure the product you use contains at least 60 percent alcohol.

Additional preventive actions
Other measures you can take to prevent the spread of shigella infection:

  • Supervise small children when they wash their hands.
  • Dispose of 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.