The bacterial infection is most common in young kids, but anyone can get it.

Shigella is a bacterial infection that causes diarrhea—and can spread like wildfire, especially in places like jails, nursing homes, and schools.

The term shigella is actually the name for a group of bacteria that cause an infection known as shigellosis. There are four types of shigella. The most common one in the U.S. is Shigella sonnei or “group D” shigella, followed by Shigella flexneri or “group B” shigella. The other two types—Shigella boydii and Shigella dysentariae—are widespread in developing countries but rare in the U.S.

Shigella bacteria cause about half a million cases each year among Americans, according to the Centers for Disease Control and Prevention (CDC). Most of these get better on their own, but the organisms can sometimes cause more serious health problems.

Shigella symptoms

The main symptom of shigella is diarrhea—and often diarrhea that is more severe than that from other stomach bugs.

“[The diarrhea] can often be bloody and can be accompanied by fever and abdominal cramping,” Kara Gross Margolis, MD, a spokesperson for the American Gastroenterological Association, tells Health.

Other shigella symptoms can include nausea, vomiting, and, rarely, seizures or post-infectious arthritis, also called reactive arthritis. Signs of this arthritis are much like those of any other form: joint pain and inflammation, often in the ankles, knees, feet, and hips. In some cases, the strain of bowel movements in someone with shigella can cause the rectum to prolapse (slip down) through the anus.

Symptoms of shigella usually show up one to two days after you’ve been infected, although some people have no symptoms at all.

Shigella causes

Shigella is passed through contaminated feces (and poop may be contagious even if a person doesn't show symptoms).

“Bacteria can spread from an infected person to water, directly to another person, or in various types of food,” says Dr. Margolis, who is also an associate professor of pediatrics in the Division of Pediatric Gastroenterology, Hepatology, and Nutrition at Columbia University Medical Center in New York City.

The most common way shigella is transmitted is directly from person to person. This can happen if you have feces on your hand (say, from changing a child’s diaper) and then touch your mouth.

Fruit, leafy greens, turkey, chicken, lunch meat, milk, and raw oysters are among the more commonly contaminated foods, says Dr. Margolis. Foods that require human preparation—like sandwiches—are also common culprits.

Shigella can also be passed through sex if you have contact with contaminated stool. It can also be spread by houseflies and water, either untreated drinking water or just swallowing a mouthful when you’re swimming in contaminated water.

Children under 5 are most at risk for shigella infection, although anyone can be infected.

Shigella prevention

Because shigella is transmitted by accidentally ingesting contaminated poop, preventing shigella is all about the tried-and-true: washing your hands. “Rigorous hygiene is of the utmost importance,” says Dr. Margolis. “It is very contagious for up to one to two weeks, even after the diarrhea has resolved.”

Hand washing is especially important after going to the bathroom and after changing diapers. You should also make sure children wash their hands thoroughly. Throw diapers away promptly, in a lined garbage can, the CDC advises. Avoid preparing food for others when you have diarrhea, and if your kids have diarrhea, keep them home from school.

Traveling to developing countries can also pose a hazard, and if you are on roads less traveled, drink only boiled or treated water and eat only cooked foods and fruit you peel yourself, according to

Shigella treatment

A mild case of shigella usually clears up on its own in five to seven days, although bowel moments may take longer to return to normal. Antibiotics can speed up the recovery process. Otherwise, you’re left with rest (preferably close to a bathroom), drinking plenty of fluids to avoid dehydration, and staying away from tempting over-the-counter remedies.

“Avoid drugs that treat diarrhea (like Imodium or Lomotil) because they can make the condition worse,” says Dr. Margolis. Bismuth subsalicylate (like Pepto-Bismol) is OK to use, however, and acetaminophen may help with a fever.

See a doctor if you or your child has a fever of 101 or higher or you show signs of dehydration like losing weight and urinating less often.

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