Shigella Infection: Signs, Symptoms and Complications

People infected with Shigella (shigellosis) usually start to feel sick 1 to 2 days after contact with the germ. Some never have symptoms at all.

Symptoms

• diarrhea, which can be bloody or prolonged (more than 3 days);
• fever;
• stomach pain;
• feeling the need to pass stool even when the bowels are empty.

Symptoms usually last 5 to 7 days, but can last anywhere from a few days to 4 weeks or more. Sometimes it takes several months for bowel habits — how often and what consistency — to return fully to normal.

When to call a doctor

Anyone with diarrhea should contact a doctor if they also have:

• fever;
• bloody or prolonged diarrhea;
• severe stomach cramps or tenderness;
• dehydration.

People in poor health, or whose immune systems are weakened by disease (such as HIV) or treatment (such as cancer chemotherapy), are more likely to be sick for longer and should contact a doctor if they have symptoms. CDC describes treatment separately.

Complications

Reactive arthritis. About 2% of people infected with certain types of Shigella, most often S. flexneri, develop reactive arthritis, with joint pain, eye irritation and painful urination. It usually affects people with a particular genetic makeup that puts them at risk. It typically lasts 3 to 5 months but occasionally persists for years and becomes chronic arthritis. It can also follow S. sonnei infection and is less common with S. boydii and S. dysenteriae.

Bloodstream infections. Around 0.4% to 7.3% of people with shigellosis develop a bloodstream infection, caused either by Shigella itself or by other gut germs that get into the blood when Shigella damages the intestinal lining. These infections are most common in people with weakened immune systems — from HIV, diabetes, cancer or severe malnutrition — and are seen more often in children and with S. flexneri and S. dysenteriae. Patients who develop one have a higher risk of death.

Seizures. Young children with shigellosis sometimes have generalized seizures, which usually stop without treatment. These children typically have a high fever, low blood sugar or abnormal blood electrolytes (salts), but why the seizures happen has not been definitively explained.

Hemolytic-uremic syndrome (HUS). HUS is a rare complication, also most common in children. Bacteria in the digestive system produce a toxin that destroys red blood cells, which then block the kidneys' filtering and can cause kidney failure. Patients often have bloody diarrhea, and HUS can be fatal. In shigellosis it is linked to Shigella strains that produce Shiga toxin, most often S. dysenteriae. It can occur when the infection is treated with drugs the bacteria resist, or when treatment starts after 4 days of symptoms, and it is the leading cause of death in S. dysenteriae outbreaks.

Sources

• Centers for Disease Control and Prevention: "Signs and Symptoms of Shigella Infection," with its cited studies. The source misspells S. dysenteriae as "dystenteriae" in two places; it is corrected here. Its stock photograph is not reproduced.