What You Need to Know About Shigella

Adapted from the Centers for Disease Control and Prevention

Shigellosis is an infectious disease caused by a group of bacteria called Shigella. Every year, about 18,000 cases of shigellosis are reported in the United States. Since many mild cases are not diagnosed or reported, the actual number of infections may be twenty times greater. Shigellosis is particularly common in settings where hygiene is poor and can sometimes sweep through entire communities. Shigella infection is more common in summer than winter. Children, especially toddlers aged 2 to 4, are the most likely to be infected by Shigella. Many cases are related to the spread of illness in child-care settings, and many more are the result of the spread of the illness in families with small children.

In the developing world, Shigella is far more common and is present in most communities most of the time.

Once someone has had shigellosis, they are not likely to get infected with that specific type of Shigella again for at least several years. However, they can still get infected with other types of Shigella.

Shigella sonnei bacteria shown in a colony
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Symptoms of Shigella Infection

Symptoms start a day or two after victims are exposed to the Shigella bacterium and usually resolve in 5 to 7 days. Some people who are infected may have no symptoms at all, but may still pass the Shigella bacteria to others. Symptoms may include:

In some people, especially young children and the elderly, the diarrhea can be so severe that the victim needs to be hospitalized.

A severe infection with high fever may also be associated with seizures in children less than 2 years old.

About 3 percent of people who are infected with one type of Shigella, Shigella flexneri, will later develop reactive arthritis. Symptoms of reactive arthritis are:

  • pain in the joints
  • irritation of the eyes
  • painful urination

Reactive arthritis is caused by a reaction to Shigella infection that happens only in people who are genetically predisposed to it. It can last for months or years, and can lead to chronic arthritis which is difficult to treat.

Treatment of Shigella Infection

Diarrhea caused by shigellosis can lead to dehydration, which may need to be treated with IV fluids. When many people in a community are affected, antibiotics are sometimes used selectively to treat only the more severe cases. Antidiarrheal agents are likely to make the illness worse and should be avoided.

Spreading Shigella

Shigella are present in the diarrheal stools of infected people while they are sick and for a week or two afterward. Most Shigella infections are passed from stools or soiled fingers of one person to the mouth of another person, usually from poor hygiene and handwashing habits, especially among toddlers who are not fully toilet-trained. Family members and playmates of such children are at high risk of becoming infected.

Shigella infections may be acquired from eating contaminated food. Shigella infections can also be acquired by drinking or swimming in contaminated water. Water may become contaminated if sewage runs into it, or if someone with shigellosis swims in it.

Preventing Shigella Infection

  • There is no vaccine to prevent shigellosis.
  • People who have shigellosis should not prepare food or pour water for others until they have been shown to no longer be carrying the Shigella bacterium.
  • Basic food safety precautions and regular drinking water treatment prevents shigellosis. At swimming beaches, having enough bathrooms near the swimming area helps keep the water from becoming contaminated.
  • Simple precautions taken while traveling to the developing world can prevent getting shigellosis. Drink only treated or boiled water, and eat only cooked hot foods or fruits you peel yourself. The same precautions prevent traveler's diarrhea in general. "Boil it, cook it, peel it, or forget it!"
  • Wash hands with soap carefully and frequently, especially after going to the bathroom, after changing diapers, and before preparing foods or beverages
  • Dispose of soiled diapers properly
  • Disinfect diaper changing areas after using them
  • Keep children with diarrhea out of child care settings
  • Supervise handwashing of toddlers and small children after they use the toilet
  • Avoid drinking pool water.
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  • Adapted from the Centers for Disease Control and Prevention (CDC) General Information on Shigellosis