Shigellosis Explained

by National Institute of Health

Shigellosis is an infectious disease, which can be spread through contaminated food and water, and is a form of dysentery (an intestinal disease). The Centers for Disease Control and Prevention (CDC) estimates more than 400,000 cases occur every year in the United States. Health care providers report about 18,000 cases to CDC each year.

Cause

Shigellosis is caused by Shigella bacteria. Four main types of Shigella cause infection: S. dysenteriae, S. flexneri, S. boydii, and S. sonnei.

Transmission

You can be infected from Shigella by eating food or drinking beverages contaminated by food handlers infected with Shigella who didn't wash their hands properly after using the bathroom, eating vegetables grown in fields containing sewage, eating food contaminated by flies bred in infected feces, swimming in or drinking contaminated water.

S. sonnei is the most common type of Shigella in developed countries, including the United States. Outbreaks of shigellosis frequently occur in tropical or temperate climates, especially in areas with severe crowding and/or poor hygiene that sometimes occur in daycare and institutional settings.

Even if you have no symptoms of shigellosis, you can still pass the bacteria to others. An extremely low number of bacteria (10 to 100) is needed to transmit the infection. Therefore, it is commonly transmitted by food handlers who are sick or infected, but have no symptoms, and who do not properly wash their hands after using the toilet. If you know you have shigellosis, you should not prepare food or beverages for others until laboratory tests show you no longer carry Shigella bacteria.

Symptoms

• Fever
• Tiredness
• Watery or bloody diarrhea
• Nausea and vomiting
• Abdominal pain

Symptoms usually begin within 2 days after you come in contact with Shigella. Symptoms usually are gone within 5 to 7 days.

Diagnosis

Laboratory tests can identify Shigella in your stool if you are infected. Sometimes, these tests are not performed unless the laboratory is instructed specifically to look for these bacteria. The laboratory can also do special tests to tell which type of Shigella you have and which antibiotics, if any, would be best to treat it.

Treatment

If you have a mild infection, you should get better quickly without taking medicine. If you need to be treated, your health care provider usually will prescribe an antibiotic such as ampicillin or ciprofloxacin. Antidiarrheal medicines may make the illness worse.

Prevention

• Wash hands with soap and water before preparing foods and beverages.
• Wash hands after using the bathroom or changing infant diapers.
• Disinfect diaper-changing areas after use.
• Help young children wash their hands carefully after they use the bathroom.
• Avoid swallowing swimming pool water.

Complications

People who have diarrhea symptoms usually recover completely, although their bowel habits may not return to normal until several months later.

S. dysenteriae type 1 bacteria produce Shiga toxin and can lead to life-threatening hemolytic uremic syndrome (HUS), which can lead to kidney failure. In North America, HUS is the most common cause of acute kidney failure in children, who are particularly prone to this complication. This life-threatening condition is usually treated in an intensive care unit of a hospital, sometimes with blood transfusions and kidney dialysis. About 8 percent of people with HUS have other lifelong complications, such as high blood pressure, seizures, blindness, paralysis, and the effects from having part of their intestines removed due to the disease.

S. flexneri infection can progress to Reiter's syndrome, which can last for months or years and can lead to chronic arthritis. Its symptoms are painful joints, irritated eyes, and painful urination.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.