Overview
Shigellosis is a bacterial infection of the large intestine that causes diarrhoea, often with blood, along with fever and stomach cramps. It takes only a very small number of bacteria to cause illness, which is why it spreads easily within households, schools and childcare settings.
CDC states that most people recover without antibiotics in 5 to 7 days. The concern now is resistance: CDC reports strains that resist all the commonly recommended antibiotics, which makes prevention and careful use of antibiotics more important than ever.
Disease Summary
- Category
- Infectious Disease
- Cause
- Shigella bacteria
- Transmission
- Faecal-oral route, contaminated food and water
- Body System
- Digestive System
- Preventable
- Yes
- Curable
- Yes
Symptoms
Common Symptoms
Symptoms usually begin one to two days after swallowing the bacteria and last about five to seven days.
Diarrhoea, Often With Blood
The defining feature. Stools may contain blood or mucus, which is what distinguishes this from most other causes of diarrhoea.
Fever
Fever is usual and often appears at the same time as the diarrhoea.
Stomach Cramps
Cramping pain in the abdomen, often severe and coming in waves.
An Urgent, Painful Need to Open the Bowels
A persistent sensation of needing to pass stool even when the bowel is empty is characteristic.
Nausea and Vomiting
Commonly accompany the diarrhoea, particularly in children.
Tiredness and Loss of Appetite
These follow from the fever and fluid loss.
Weight Loss
Occurs where the illness is prolonged or in a child who was already underweight.
Bacteria in the Stool After Recovery
People can keep passing the bacteria for weeks after they feel better, which is why hygiene matters beyond the illness itself.
Danger Signs
Seek urgent medical attention immediately if any of the following symptoms develop.
Signs of Dehydration
Very little urine, sunken eyes, drowsiness, or in a child no tears when crying. This is the commonest cause of death from this infection.
Seizures in a Child
Seizures can occur with high fever in young children with this infection and need emergency assessment.
Severe Abdominal Pain With a Swollen Abdomen
This can indicate a serious complication of the colon and is a surgical emergency.
Reduced Urine With Pallor and Bruising
This combination can indicate a rare but serious kidney complication and needs immediate care.
High Fever With Confusion
Confusion or drowsiness with a high fever needs same-day assessment, particularly in a child.
Diagnosis
The Clinical Picture
Diarrhoea with blood, fever and cramps in someone with a plausible exposure points strongly towards it, though it cannot be confirmed on symptoms alone.
Stool Testing
A stool sample identifies the bacteria and distinguishes it from the other causes of bloody diarrhoea, which need different treatment.
Antibiotic Sensitivity Testing
Because resistance is now common, testing which antibiotics will work has become an essential part of diagnosis rather than an optional extra.
Identifying the Source and Contacts
Household members, childcare contacts and shared food or water are traced, because a very small number of bacteria transmits the infection.
Assessing Hydration
How dehydrated a person is determines the urgency of treatment more than the diagnosis itself does.
Laboratory Tests
Stool Culture
Grows the bacteria and identifies which type it is. This remains the test that also allows antibiotic sensitivity to be measured.
Molecular Stool Test
Detects the bacteria’s genetic material quickly, often as part of a panel covering several causes of diarrhoea. A culture is still needed for sensitivity testing.
Antibiotic Sensitivity Testing
Shows which antibiotics will work. CDC reports that resistance to the commonly recommended antibiotics is now widespread in several parts of the world.
Blood Tests for Salts and Kidney Function
Used where dehydration is significant, to guide fluid replacement and detect complications.
Stool Examination for Parasites
Done alongside, because amoebiasis causes very similar bloody diarrhoea and needs completely different treatment.
Treatment
Rehydration
The most important treatment. Replacing fluid and salts is what prevents death from this infection, particularly in children.
Continued Feeding
Children should keep eating and breastfeeding through the illness. Withholding food prolongs recovery and worsens nutrition.
Rest and Time
CDC states that people with this infection usually get better without antibiotic treatment in 5 to 7 days.
Antibiotics for Severe or High-Risk Cases
Reserved for severe illness, for young children, for older adults, and for people whose immune systems are weakened. The choice depends on local resistance patterns.
Hospital Care
Needed where dehydration is severe, where the person cannot keep fluids down, or where complications develop.
Prevention
Wash hands thoroughly with soap and water
Especially after using the toilet, changing nappies and before preparing food. This is the single most effective measure.
Drink safe water
Boiled, bottled or properly treated water, particularly where sanitation is poor.
Careful food handling
Wash, peel or cook produce, and keep people with diarrhoea away from food preparation.
Keep children with diarrhoea home
CDC identifies childcare settings as a common place for spread, and a very small number of bacteria is enough to transmit it.
Do not swallow recreational water
Lakes, rivers and pools can carry the bacteria, particularly during an outbreak.
Avoid sex until well after recovery
CDC advises abstaining from sexual contact for at least two weeks after diarrhoea ends, because the bacteria continue to be shed.
Risk Factors
Young Children
CDC states that most cases and deaths occur among children.
- Children under five, who are most likely to become severely dehydrated
- Children in nurseries and childcare settings
- Children still in nappies
- Malnourished children, in whom the illness is more severe and lasts longer
Households and Institutional Settings
A very small number of bacteria is enough to transmit the infection.
- Household members of someone who is ill
- People in crowded residential settings
- Carers changing nappies or helping with toileting
- Food handlers, who can start an outbreak
People With Weakened Immune Systems
Illness is more severe and lasts longer in this group.
- People living with untreated HIV
- People on treatment that suppresses the immune system
- Older adults
- People with existing chronic illness
Travellers and Specific Communities
CDC identifies particular routes and groups in recent outbreaks.
- Travellers to areas with poor sanitation
- Communities without safe water
- Men who have sex with men, among whom CDC has reported resistant strains
- People experiencing homelessness
Complications
Dehydration
The commonest and most dangerous complication, and the reason most deaths occur.
Seizures
Young children with high fever from this infection can have seizures, which is frightening but usually not a sign of lasting harm.
Damage to the Colon
Severe infection can cause the colon to become inflamed and dilated, which is a surgical emergency.
A Rare Kidney Complication
Some strains can trigger a serious condition affecting the blood and kidneys, particularly in children.
Joint Pain After the Infection
A minority of people develop joint pain and eye irritation weeks after recovering.
Drug-Resistant Infection
CDC reports strains resistant to all commonly recommended antibiotics, which makes treatment of severe cases considerably harder.
When to Seek Medical Care
Any Diarrhoea With Blood
Bloody diarrhoea always needs assessment, because the causes differ and so do the treatments.
Signs of Dehydration
Very little urine, sunken eyes, drowsiness, or no tears in a crying child. Start oral rehydration solution and seek care.
A Seizure, Confusion or Unusual Drowsiness
Particularly in a child with fever and diarrhoea.
Severe Abdominal Pain With Swelling
This may indicate a complication of the colon and is an emergency.
Diarrhoea Lasting More Than a Week
Prolonged illness needs testing and review.
Prognosis
Most People Recover Without Antibiotics
CDC states that people with this infection usually get better without antibiotic treatment in 5 to 7 days.
Outcome Depends on Rehydration
Deaths result from fluid loss rather than from the bacteria themselves, which is why oral rehydration solution matters so much.
Bacteria Are Shed After Recovery
People can keep passing the bacteria for weeks after feeling well, so hygiene precautions continue after the diarrhoea stops.
Resistance Is Making Treatment Harder
CDC reports a rising share of infections caused by strains resistant to all commonly recommended antibiotics.
Differential Diagnosis
Amoebiasis
Also causes bloody diarrhoea, and is treated with completely different medicines. A stool test separates them.
Other Bacterial Causes of Bloody Diarrhoea
Several bacteria produce a very similar illness and are separated by stool culture.
Typhoid Fever
Causes prolonged fever with abdominal symptoms, and is separated by blood culture.
Inflammatory Bowel Disease
Causes bloody diarrhoea over months rather than days, and is diagnosed by endoscopy.
Malaria
In endemic areas, fever with abdominal symptoms must also be tested for malaria, which can be present at the same time.
References
CDC: About Shigella Infection
Symptoms, transmission, who is at risk and how long people remain infectious.
CDC: Clinical Overview of Shigellosis
Clinical features, complications, diagnosis and antibiotic resistance patterns.
CDC: Treatment of Shigella Infection
When antibiotics are indicated, rehydration, and what to avoid.
World Health Organization: Shigella
Global and regional burden, the impact on children, and vaccine development.
Frequently Asked Questions
Do I need antibiotics for shigellosis?
Usually not. CDC states that people with this infection usually get better without antibiotic treatment in 5 to 7 days. Antibiotics are reserved for severe illness, young children, older adults and people whose immune systems are weakened, and the choice depends on local resistance patterns.
Can I take something to stop the diarrhoea?
Not when there is blood in the stool or a fever. Medicines that stop diarrhoea can trap the infection and make the illness worse. Oral rehydration solution is the right treatment.
How long am I infectious?
Longer than you feel ill. People can keep passing the bacteria in stool for weeks after recovering. CDC advises careful handwashing throughout and abstaining from sexual contact for at least two weeks after the diarrhoea ends.
Why is drug-resistant shigella a concern?
Because CDC reports strains resistant to all the commonly recommended antibiotics, and the share of infections caused by such strains has risen in recent years. This is why antibiotics are reserved for those who need them and why sensitivity testing matters.
Is there a vaccine?
No. CDC states that no vaccine is available. WHO lists Shigella as a priority for vaccine development, particularly for young children in low- and middle-income countries, but none is licensed yet.