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Medically reviewed by Last updated on Feb 19, 2024.

What is Shigellosis?

Harvard Health Publishing

Shigellosis is an infection of the colon (large intestine) caused by Shigella bacteria. Shigellosis is also 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. Bacteria 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. Shigella bacteria can reach 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. 

Shigellosis is more common among children ages 1 to 4. Children of this age have a higher rate of infection because they are starting to use the toilet and often forget to wash their hands. Infants are at the highest risk of becoming seriously ill from a Shigella infection. 


Although health experts don't know why, some people take in Shigella bacteria without becoming ill. Others develop only a brief fever, or a brief fever 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 people can have 10 to 30 bowel movements each day, along with a persistent urge to have a bowel movement. 

Rarely, Shigella bacteria can affect other parts of the body far from the digestive tract. When this happens, there may be a rash, joint pain, confusion and/or kidney failure.


Your doctor will ask about your symptoms and about the appearance of your bowel movements. He or she will ask if you have recently traveled to developing countries, been in contact with people who have severe diarrhea, or might have been exposed to contaminated pools, lakes or food.  

Your doctor will diagnose shigellosis based on a physical examination and the results of laboratory tests. These tests include taking a swab of your rectum or a sample of your stool (feces). If you have signs of dehydration (excessive loss of body water) or significant blood loss, additional blood tests may be necessary. 

Expected Duration

In most otherwise healthy people with mild shigellosis, diarrhea goes away on its own within five to seven days. However, in very young children, the elderly or people with chronic illnesses, shigellosis can be severe and can lead to life-threatening dehydration and other complications within a few days. 


There is no vaccine to protect against shigellosis. To prevent the spread of Shigella bacteria, you should: 


If you have a mild case of shigellosis, you probably won't need treatment because your symptoms will probably go away on their own. Doctors may prescribe antibiotics if there are very young or very old members in your household who could get the infection.  

If you have a severe case of shigellosis, your doctor will prescribe fluids to treat dehydration and an antibiotic. Many strains of Shigella have developed resistance to multiple antibiotics. Your doctor will choose an antibiotic based on how and where you became infected.  

The use of antidiarrheal medicines to slow bowel movements is controversial because it can take longer to clear the bacteria from the lower intestine. This could potentially cause the infection to become more severe. 

Treatment options

The following list of medications are related to or used in the treatment of this condition.

View more treatment options

When To Call a Professional

Call your doctor if you develop severe diarrhea, especially if the bowel movements contain blood or mucus. Call your doctor whenever you have a fever and severe diarrhea. Seek immediate attention if you have signs of dehydration, such as very dry mouth and lips, and lightheadedness when you stand, whether or not you are thirsty. 


In developed countries, most people with shigellosis recover completely. In underdeveloped countries, the risk of complications, including death, is significantly higher.

Additional Info

Centers for Disease Control and Prevention (CDC)

Learn more about Shigellosis

Treatment options

Care guides

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.