Shigella infection is an illness that affects the intestine. Another name for it is shigellosis. It's caused by a group of germs called shigella bacteria.

Children under age 5 are most likely to get shigella infection. But the illness can happen at any age. The germs that cause it spread easily through an infected person's stool. The germs can get on fingers, on surfaces, or into food or water. Infection happens after the germs are swallowed.

The main symptom of shigella infection is diarrhea that can be bloody or long lasting. Other symptoms can include fever and stomach pain.

Most often, shigella infection clears up on its own within a week. Treatment for serious illness may include medicines called antibiotics that get rid of the germs.

Help prevent shigella infection by washing hands often, especially after changing a diaper or using the bathroom. And if you swim in ponds, lakes or swimming pools, try not to swallow the water.

Symptoms of shigella infection usually start a day or two after contact with the germs that cause it. Sometimes, the illness takes up to a week to start.

Symptoms can include:

• Diarrhea that may contain blood or mucus, and that may last more than three days.
• Stomach pain or cramps.
• A feeling of needing to pass stool even when the bowel is empty.
• Fever.
• Upset stomach or vomiting.

Symptoms tend to last up to seven days. Sometimes they last longer. Some people have no symptoms after they've been infected with shigella. But the germs may be able to spread through the stool for up to a few weeks.

When to see a doctor

Call your healthcare professional or seek urgent care if you or your child has:

• Bloody diarrhea.
• Diarrhea that causes weight loss and dehydration.
• Diarrhea along with a fever of 102 degrees Fahrenheit (39 degrees Celsius) or higher.
• Terrible stomach cramps or tenderness.
• Frequent vomiting that prevents you from keeping down liquids.
• Dehydration symptoms such as little or no urination, very dry mouth and throat, or a feeling of dizziness when standing.

If you have a weakened immune system, call your healthcare professional if you have any shigella infection symptoms. The illness is more likely to make you sick for a longer time.

Shigella infection is caused by swallowing shigella bacteria. This can happen when you:

• Touch your mouth. This poses a risk because there are many ways for shigella germs to get on your hands. You might change the diaper of a child who has shigella infection. Or you might touch an object that has germs on it, such as a toy or changing table. The germs also can spread from hand to mouth during sexual contact with someone who has the infection.
• Eat tainted food. A person with a shigella infection who handles food can spread the germs to people who eat the food. Food also can become tainted if it grows in a field that contains sewage.
• Swallow tainted water. Water can become tainted with shigella germs from sewage. Water also can become tainted if a person with shigella infection swims in it.

Risk factors for shigella infection include the following:

• Being a child. Children under age 5 are most likely to get shigella infection. But people of any age can get the illness.
• Living in group housing or doing group activities. Close contact with other people can spread the germs from person to person. Shigella outbreaks are more common in child care centers, schools, public pools, water parks and nursing homes.
• Living or traveling in areas that lack clean water and sewage disposal services. People who live or travel in developing countries are more likely to get shigella infection.
• Sexual contact that involves the anus. Shigella germs can spread from the stool or soiled fingers of one partner to the mouth of another partner. This puts men who have sex with men at higher risk of shigella infection.
• Experiencing homelessness. This may involve staying in crowded areas or having less access to clean water and toilets. That can raise the risk of infection when shigella germs are spread through the community.
• Having a weakened immune system. This raises the risk of more-serious shigella infection. The immune system may be weakened from health conditions such as HIV or from treatments such as chemotherapy.

It may take weeks or months before you return to your typical bowel habits. And most often, shigella infection clears up without leading to other health conditions called complications.

Dehydration

Constant diarrhea can cause dehydration. Symptoms include dizziness, lack of tears in children, sunken eyes and dry diapers. Serious dehydration can lead to shock and death.

Seizures

Some children with shigella infections have seizures. Seizures can cause changes in behavior, jerking movements and loss of consciousness. They are more common in children who have high fevers. But they also can happen in children who do not have high fevers.

It's not known whether the seizures are a result of the fever or the shigella infection itself. If your child appears to have a seizure, call your healthcare professional right away.

Rectal prolapse

This condition happens when part of the large intestine's lowest section slips outside the anus. It may be more common in children with shigella who don't get enough nutrition.

Hemolytic uremic syndrome

This rare complication of shigella affects the blood and blood vessels. It can lead to kidney failure.

Toxic megacolon

This rare complication prevents the colon from passing stool and gas. The colon becomes bigger as a result. Symptoms include stomach pain and swelling, fever, and weakness. Without treatment, the colon may burst. This causes a life-threatening infection called peritonitis that needs emergency surgery.

Reactive arthritis

This condition can happen weeks after shigella infection. Symptoms include joint pain and swelling, usually in the ankles, knees, feet and hips. Other symptoms can include painful urination and redness, itching, and discharge in one or both eyes.

Bloodstream infection

This also is known as bacteremia. Shigella infection can damage the lining of the intestines. Rarely, shigella germs enter the blood through the damaged lining and cause a bloodstream infection. These infections are more common in adults with weakened immune systems and in children.

Take the following steps to help prevent shigella infection:

• Wash hands often. Use soap and water, and scrub for at least 20 seconds. This is key before you prepare or eat food, and before sexual activity. It's also important to wash after you use the bathroom or change a diaper.
• Throw away soiled diapers in a covered, lined garbage can.
• Disinfect diaper-changing areas right after use, especially if the diaper leaks or spills.
• Try not to swallow water from ponds, lakes or untreated pools.
• Do not have sexual contact with anyone who has diarrhea or who recently recovered from diarrhea. Wait at least two weeks.

If you or your child has diarrhea or a known shigella infection, take these steps to prevent spreading germs:

• Keep washing hands often. And watch small children when they wash their hands.
• Don't prepare food for others if possible.
• Stay home from healthcare, food service or child care jobs while sick.
• Keep children with diarrhea home from child care, play groups or school.
• Don't go swimming until you have fully recovered.

Diagnosis of shigella infection involves a physical exam and testing to find out if you have the illness. Many other health conditions can cause diarrhea or bloody diarrhea.

You or your healthcare professional collects a sample of your stool. Then a lab checks the sample for shigella germs or for harmful substances called toxins that the germs make.

Treatment for shigella infection depends on how serious the illness is. Most often, the illness is mild and gets better within seven days. You may only need to replace lost fluids from diarrhea, especially if your overall health is good.

Medicines sold without a prescription

Talk to your healthcare professional before you take any diarrhea medicine that's sold without a prescription. Many conditions can cause diarrhea, and these medicines could make some conditions worse.

If a lab test has confirmed that you have shigella infection, medicine that contains bismuth subsalicylate (Pepto-Bismol, Kaopectate) may help. This is available without a prescription. It may help you pass stool less often and shorten the length of your illness. But it isn't recommended for children, pregnant or breastfeeding people, or people who are allergic to aspirin.

Do not take diarrhea medicines such as loperamide (Imodium A-D). Also, do not take medicines that contain the combination of diphenoxylate and atropine (Lomotil). These aren't recommended for shigella infection. They can lower the body's ability to clear shigella germs and make your condition worse.

Antibiotics

For a serious shigella infection, your healthcare professional may recommend medicines called antibiotics that help get rid of germs. Antibiotics may shorten the length of the illness. But some shigella bacteria resist the effects of these medicines. So your healthcare professional may not recommend antibiotics unless your shigella infection is very bad.

Antibiotics also may be needed to treat infants, older adults and people with weakened immune systems. Antibiotics also may be used if there's a high risk of spreading the disease.

If you're given antibiotics, take them exactly as prescribed. Finish taking all the pills even if you start to feel better.

Fluid and salt replacement

For adults in good health overall, drinking water may be enough to prevent dehydration caused by diarrhea.

Children may benefit from a treatment called oral rehydration solution, such as Pedialyte. This is sold in drugstores and taken by mouth. Many pharmacies carry their own brands.

Children and adults who are very dehydrated need treatment in a hospital emergency room. Treatment involves salts and fluids given through a vein rather than by mouth. This is called intravenous hydration. It provides the body with water and essential nutrients much more quickly than oral solutions do.

Many people who have shigella infection get better without medicines. But if you or your child has serious symptoms or a high fever, call your healthcare professional. You may need treatment.

What you can do

Before talking with your healthcare professional, write a list of answers to the following questions:

• What are the symptoms?
• When did the symptoms start?
• Have you or your child been exposed to a person who has or had shigella infection?
• Do you or your child have a fever? If so, how high is it?

What to expect from your doctor

During the physical exam, your healthcare professional may press on parts of your stomach area. This is done to check for pain or tenderness. Your healthcare professional also may use a cotton swab to get a stool sample. Or you may be given instructions on how to collect and send a sample of your stool to a lab for testing.