Most stomach bugs come and go without much fuss. Shigella is different, partly because it spreads so easily and partly because it can cause bloody diarrhea that frightens people into thinking something is seriously wrong. Often it isn’t dangerous. But it is worth recognizing, because the way you handle it affects how soon you recover and whether you pass it to someone else.
In short: Shigella infection (also called shigellosis) is an intestinal infection caused by Shigella bacteria. It spreads through contact with the stool of an infected person, and most healthy people recover within a week.
What Is Shigella Infection?
Shigella bacteria live in the intestines of infected people and leave the body in stool. Humans are the only natural reservoir for Shigella, so every case traces back to another person. Doctors also use the older term “dysentery” for this kind of bloody, mucus-filled diarrhea.
How Shigella Spreads
It takes very little to get sick. Only a small amount of the germ, too small to see, can make someone ill. The CDC explains that transmission happens when people put something in their mouths, or swallow something, that has come into contact with the stool of someone infected. In everyday life, that usually looks like this:
- Dirty hands. Getting Shigella on your hands and then touching your food or mouth.
- Food. Eating food prepared by someone who is infected. Foods eaten raw are more likely to be contaminated, and fruits and vegetables can pick up the germ from fields contaminated with stool.
- Water. Swallowing water while swimming is a recognized risk, particularly in lakes, pools and splash areas that are poorly maintained.
- Close contact. Households, child care centers and sexual contact (see our guide on sexually transmitted diarrhea disease).
One detail surprises people: you can stay contagious after you feel better. People can shed the bacteria in their stool for up to two weeks after symptoms have gone away.
Shigella Symptoms
Symptoms usually appear one to two days after contact with the germ. The most common are:
- Diarrhea that can be bloody or prolonged (lasting more than three days)
- Fever
- Stomach pain or cramps
- A feeling of needing to pass stool even when the bowels are empty
The stools tend to be small in volume. Severe dehydration is rare, although it can still happen, especially in young children.
How long does it last? Symptoms usually last five to seven days, but some people feel unwell for a few days or for four weeks or more, and it may take several months for bowel habits to return to normal. And some people have no symptoms at all, which is how infections spread quietly.
What Causes Bloody Diarrhea in Shigella?
Shigella invades the lining of the large intestine and causes inflammation there. That irritation leads to mucus, small amounts of blood, and the urgent, crampy need to go. Bloody diarrhea has other causes too, such as other bacterial infections, parasites and bowel conditions, which is why a stool test matters rather than guessing.
Shigella Infection in Children
Children are hit harder than most. The American Academy of Pediatrics says children aged 2 to 4 are particularly vulnerable, and the incubation period is usually 2 to 4 days. The germs spread easily through day care centers and among people who live together. Children are more likely to be infected and to have severe symptoms, such as seizures.
The seizure risk can sound alarming, but the CDC says they usually go away without treatment and are typically linked to a high fever, low blood sugar or abnormal blood salts. Still, a child who has a seizure needs medical attention.
Call your pediatrician if you notice blood in your child’s stool, the diarrhea isn’t improving, or your child shows signs of dehydration.
Who Should Be Especially Careful?
- Young children and anyone in daycare settings.
- Older adults and people with weakened immune systems. Shigella can cause more severe illness in infants, older adults and people with weakened immune systems. In severe cases the infection can spread into the blood, which can be life-threatening.
- Travelers. International travelers and men who have sex with men are also at higher risk.
How Is Shigella Diagnosed?
Symptoms alone can’t confirm it. Healthcare providers can order laboratory tests to find Shigella in a sick person’s stool. Testing can use a culture or a culture-independent test, and a positive rapid test is usually confirmed with a stool culture. That culture also shows which antibiotics will work, which matters more than ever.
Shigella Treatment
Most people need rest and fluids, not antibiotics. Most people get better within five to seven days without medical treatment, and should drink plenty of fluids to prevent dehydration.
Antibiotics are used selectively. They are given to moderately to severely ill and high-risk patients, for example those with bloody diarrhea or a weakened immune system, and may shorten the illness and reduce contagiousness. But the choice isn’t simple. When treatment is needed, doctors choose a drug based on the susceptibility results for the individual isolate. The CDC has reported a rise in extensively drug-resistant Shigella in the US, which limits treatment options.
At home:
- Drink small, frequent sips of water or oral rehydration solution.
- Rest, and eat bland foods when you feel ready.
- Ask a doctor or pharmacist before taking anti-diarrhea medicine, especially if there is blood or fever. It can keep the infection in your gut longer.
- Never take leftover antibiotics.
Shigella Prevention
Good hygiene is the most reliable defense:
- Wash your hands with soap and water after using the toilet or changing diapers, and before preparing or eating food. Hand sanitizer isn’t a full substitute.
- Keep sick people away from others. Infected children with symptoms should not have contact with uninfected children.
- Don’t prepare food for others while you have diarrhea, and for a while after.
- Avoid swallowing water when swimming, and keep anyone with diarrhea out of pools.
- Wash raw fruits and vegetables, and be careful with food and water when traveling.
- Clean up diaper changing areas, toilets and shared surfaces thoroughly.
Possible Complications
Most people recover fully, but problems can follow. These include dehydration, post-infectious (reactive) arthritis, which only happens in people who are genetically predisposed, and, rarely in children, a kidney complication called hemolytic uremic syndrome.
Common Mistakes to Avoid
- Assuming it’s “just a stomach bug” when there’s blood in the stool.
- Taking anti-diarrhea medicine without asking a doctor.
- Going back to work, school or daycare too soon, while still contagious.
- Skipping handwashing because you feel better.
- Using leftover antibiotics, which can fuel resistance.
When to See a Doctor
Contact a doctor if you or your child has:
- Bloody diarrhea
- Diarrhea lasting more than three days
- A high fever
- Signs of dehydration: very little urine, dizziness, dry mouth, or no tears in a child
- Severe stomach pain
- A seizure
- A weakened immune system
Go to urgent care if you can’t keep fluids down or you feel very unwell.
Frequently Asked Questions
What is Shigella infection?
It’s an intestinal infection (shigellosis) caused by Shigella bacteria. It causes diarrhea, often bloody, along with fever and stomach cramps.
How does Shigella spread?
Through contact with the stool of an infected person, usually via unwashed hands, contaminated food or water, or close contact.
How long does Shigella last?
Usually five to seven days, though some people take longer to fully recover.
Is Shigella contagious after symptoms stop?
Yes. The bacteria can remain in stool for up to two weeks after symptoms go away, so keep washing your hands carefully.
Does Shigella cause bloody diarrhea?
It can. Bloody or mucus-filled diarrhea is common, but see a doctor to confirm the cause.
Do you always need antibiotics for Shigella?
No. Many people recover without them. Antibiotics are used for more severe illness or high-risk patients.
How is Shigella diagnosed?
With a stool test, usually a culture.
Is Shigella dangerous for children?
It can be more severe in young children, who are more likely to have high fever or seizures. Call your pediatrician if you notice blood in the stool or signs of dehydration.
The Bottom Line
Shigella infection is common, highly contagious and usually short-lived. Fluids, rest and careful handwashing handle most cases. Bloody diarrhea, a high fever, or illness in a baby, an older adult or someone with a weakened immune system deserves a call to the doctor.
Related reading: Salmonella: Everything You Need to Know
Sources
- CDC: Signs and Symptoms of Shigella Infection
- CDC: How Shigella Spreads
- CDC: Clinical Overview of Shigellosis
- HealthyChildren.org (AAP): Shigella Infections
- Merck Manual (consumer): Shigellosis
- Merck Manual (professional): Shigellosis
This article is for general information only and is not medical advice. See our Medical Disclaimer.