Shigellosis is infection by the gram-negative bacteria Shigella. It results in watery diarrhea or dysentery (the frequent and often painful passage of small amounts of stool that contain blood, pus, and mucus).
Shigella bacteria are excreted in stool and can be easily spread when hygiene or sanitation is inadequate.
People may have watery diarrhea, sometimes leading to severe dehydration.
Identifying the bacteria in a sample of stool can confirm the diagnosis.
Fluids are given by mouth or, if the infection is severe, intravenously.
Antibiotics are used for people who have a severe infection or those who have a weakened immune system.
For people with shigellosis and people who care for them, meticulous hygiene is necessary to avoid spreading the infection.
(See also Overview of Bacteria.)
Shigella bacteria are a common cause of dysentery in the United States and throughout the world.
Because stomach acid does not easily destroy these bacteria, ingesting even a small number of them causes infection. In the large intestine, the bacteria cause inflammation, and because they are then excreted in stool,
Infection spreads easily from person to person when hands are soiled.
Infection can occur if people touch their mouth after touching an object (such as a diaper or toy) contaminated by infected stool. People can become infected if they consume food contaminated by infected food handlers who do not wash their hands with soap after using a toilet. All such transmission involving infected stool is termed fecal-oral transmission.
Infection can spread between men who have sex with men.
Infection is also spread through the following:
Water contaminated with human waste
Ponds, lakes, or swimming and wading pools that are inadequately chlorinated
Infection easily spreads among people who live together. Outbreaks also occur in places that are overcrowded and have inadequate sanitation, such as
Day care centers for children
Long-term care facilities
Refugee camps
Institutions for the intellectually disabled
Cruise ships
Military camps
Countries where sanitary conditions are poor
Children are more likely to become infected and to have severe symptoms, such as seizures.
There are 4 species of Shigella. All cause diarrhea. However, one—Shigella dysenteriae—is more likely to cause severe diarrhea, dysentery, and complications.
Symptoms of Shigellosis
Mild infections cause a low fever (about 100.4 to 102° F [38 to 38.9° C]) and watery diarrhea 1 to 4 days after people are infected by the bacteria. Some adults do not have a fever. Mild infections in adults usually resolve in 4 to 8 days.
In adults, the first symptoms may be painful abdominal cramps and a frequent urge to defecate. Passing stool may temporarily relieve the pain. These symptoms may become more severe and occur more frequently as the infection progresses.
Severe infections may cause a low or moderate fever and watery diarrhea that progresses to dysentery. In dysentery, bowel movements are frequent and contain blood, pus, and mucus. Severe infections usually resolve in 3 to 6 weeks.
In young children, symptoms begin suddenly. Symptoms include fever, irritability or drowsiness, loss of appetite, nausea or vomiting, diarrhea, and abdominal pain. Children may frequently feel an urgent need to defecate. Within 3 days, blood, pus, and mucus appear in stool. Unless complications develop, symptoms usually resolve by the second week in children who are treated.
Complications of shigellosis
Children, particularly young children, are most likely to have severe complications:
High fever (up to 106° F [41° C]), sometimes with delirium, seizures, or coma, typically because of bacteremia
Severe dehydration with weight loss
20 or more bowel movements a day
With severe diarrhea, protrusion of part of the rectum out of the body (rectal prolapse)
Rarely, marked swelling of the intestine and tearing (perforation) of the large intestine
Hemolytic-uremic syndrome if the infection is due to Shigella dysenteriae type 1 (which is rare in the United States)
In hemolytic-uremic syndrome, red blood cells are destroyed, causing anemia with fatigue, weakness, and light-headedness. Blood clots abnormally, causing the kidneys to stop fully functioning. Seizures or strokes can also occur.
Severe dehydration can lead to shock and death, mainly in children under 2 years, and in older adults who are weakened by a chronic illness or undernutrition.
Some adults develop reactive arthritis (inflammation of the joints). Inflammation of the eyes (uveitis) and urethra (causing painful urination) may occur weeks to months after the diarrhea.
Diagnosis of Shigellosis
Culture of a stool sample
Polymerase chain reaction (PCR) testing
A doctor suspects shigellosis based on the typical symptoms of pain, fever, and watery or bloody diarrhea in people who are likely to have been exposed to the bacteria.
To confirm the diagnosis of shigellosis, doctors take a sample of stool and send it to a laboratory to grow (culture) and identify the bacteria.
Doctors may use the PCR technique to increase the amount of the bacteria's DNA, so that the bacteria can be detected more quickly.
Bacteria are also tested to see which antibiotics are effective (a process called susceptibility testing).
Treatment of Shigellosis
Fluids containing salt
For severe infections, antibiotics
Water and salts lost because of diarrhea are replaced with fluids given by mouth or, if the infection is serious, by vein.
Mild infections typically resolve without treatment. Antibiotics are not routinely required for healthy adults with mild infection.
However, doctors often give antibiotics to certain people, including those who
Are very young or very old
Have a weakened immune system
Have a moderate to severe infection
Severe infections
Prevention of Shigellosis
Prevention includes the following:
All people should wash their hands after using a toilet, before preparing food, and before sexual activity.
People should avoid sex or practice safe sex.
People should stay home from work until at least 2 days after diarrhea stops.
Infected people should not prepare food for others.
After using the toilet, infected people should wash their hands, and someone should clean and disinfect the toilet before it is used again.
People caring for people with shigellosis should wash their hands with soap and water, particularly before they touch other people or handle food.
Infected children with symptoms should not have contact with uninfected children.
Diapers of infected children should be disposed of in a sealed garbage can, and the area used to change diapers should be wiped with disinfectant after each use.
Stool that contaminates clothing, sheets, and blankets of infected people should be flushed away in running water, and the soiled items should be washed in a washing machine using the hot water cycle. When finished, surfaces of the sink, toilet, and washing machine should be wiped down with a disinfectant, such as diluted chlorine bleach.
Infected people should not go swimming.
People should discuss with their doctor how long they need to isolate and take other precautions. Precautions may be required for several weeks.
Currently, no vaccine is available, but one is being studied.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Centers for Disease Control and Prevention (CDC): Shigellosis: A resource providing information about shigellosis, including sources of infection and prevention
