What Is Shigella? Symptoms, Causes and Treatment Explained

Diarrhoea, stomach cramps and fever are common symptoms of a stomach infection, but could shigella be the cause? This highly contagious bacterium causes an intestinal infection called shigellosis, which spreads through contaminated hands or surfaces, food, water or sexual contact. Although most people recover within a week, recognising the symptoms early can help prevent further transmission. In this article, you'll learn what shigella is, how it spreads, its possible complications and when to seek medical advice.

Table of Contents

• What is shigella?

• Why is recognising a shigella infection important?

• What are the typical symptoms of a shigella infection?

• What causes a shigella infection?

• What are the possible complications of a shigella infection?

• What should you do if you suspect a shigella infection?

• How can you test for a shigella infection?

• Key takeaways about shigella infections

What is shigella?

Shigella is a group of bacteria that causes an intestinal infection known as shigellosis. There are four main species: Shigella sonnei, Shigella flexneri, Shigella boydii and Shigella dysenteriae. 

Shigella bacteria occur worldwide, but infections are more common and can be more severe in tropical and subtropical regions. In the Netherlands, approximately 400–600 cases of shigellosis are reported each year. Men who have sex with men are at increased risk of infection. Since 2022, an antibiotic-resistant strain of shigella has also been circulating in the Netherlands, primarily affecting this group. Over a two-year period, 62 cases involving this strain were reported, including 56 men.

Source: Mayo Clinic, 2024; CDC, 2024; RIVM, n.d.

Why is recognising a shigella infection important?

Recognising a shigella infection early is important to prevent further transmission, because shigella spreads easily through contaminated hands or surfaces, food, water or sexual contact. Early recognition allows people to take appropriate hygiene precautions, seek medical care when needed and reduce the risk of infecting others.

Certain groups have a higher risk of getting a shigella infection or developing serious illness.

• Higher risk of infection: People travelling to warm countries, household members of infected people (especially children), and men who have sex with men.

• Higher risk of serious illness: Children, adults over 65, people with serious underlying illnesses or weakened immune systems (including HIV), those infected with Shigella dysenteriae, and people taking medication that slows bowel movements.

Source: RIVM, n.d.

What are the typical symptoms of a shigella infection?

Shigella symptoms usually appear within one to two days of exposure, although they can sometimes take up to a week to develop. Some people experience mild discomfort, while others develop more noticeable problems.

Common symptoms of a shigella infection include:

• Diarrhoea: Frequent, loose stools that may contain blood or mucus and sometimes last longer than three days.

• Stomach pain or cramps: Abdominal discomfort that can range from mild to severe.

• Fever: A raised body temperature, sometimes accompanied by chills.

• Frequent urge to use the toilet: Feeling the need to pass stool even when the bowel is empty.

• Nausea or vomiting: Feeling sick or occasionally vomiting.

Most people recover within five to seven days, although symptoms may last longer in some cases. Some people experience no symptoms at all but can still spread the bacteria through their stool. Shigella can remain in the stool for several weeks after symptoms have disappeared, making good hygiene important even after recovery.

Source: Mayo Clinic, 2024; CDC, 2024

What causes a shigella infection?

Shigella spreads through the faecal-oral route, meaning tiny amounts of infected stool enter another person's mouth. The bacteria are highly contagious and can spread through contaminated hands or surfaces, food, water or sexual contact.

The main transmission routes include:

1. Person-to-person contact: Touching contaminated surfaces, such as toilet seats, taps, door handles or toys, and then touching your mouth or food. Changing nappies or caring for someone with shigellosis also increases the risk.

2. Contaminated food: Eating food prepared by someone with a shigella infection, particularly foods eaten raw. Fruit and vegetables can also become contaminated during growing or handling.

3. Contaminated water: Drinking water contaminated with infected stool or accidentally swallowing contaminated water while swimming in lakes, rivers or other recreational waters.

4. Sexual contact: Sexual activities involving contact with infected stool, including anal sex or the use of contaminated sex toys.

Source: CDC, 2024; RIVM, n.d.

How long is shigella contagious?

People with shigellosis can continue to pass bacteria in their stool for several weeks, even after symptoms disappear. This means they may still infect others when they feel better. Good hygiene remains essential during recovery and afterwards to prevent further transmission.

Source: CDC, 2024; RIVM, n.d.

What are the possible complications of a shigella infection?

Most shigella infections clear up within a week without serious complications, although bowel habits may take several weeks to return to normal. In some cases, however, the infection can lead to:

1. Dehydration: Frequent diarrhoea can cause excessive fluid loss, leading to dizziness, dry mouth and reduced urination. Severe dehydration can be life-threatening if left untreated.

2. Seizures: Some children may experience seizures during a shigella infection, sometimes associated with high fever.

3. Rectal prolapse: Repeated straining during diarrhoea can cause part of the rectum to protrude through the anus, particularly in malnourished children.

4. Haemolytic uraemic syndrome (HUS): A rare but serious condition that affects the blood and kidneys and can lead to kidney failure.

5. Toxic megacolon: A rare, severe swelling of the colon that can cause serious complications if left untreated.

6. Reactive arthritis: Joint pain and swelling that may develop weeks after the infection, sometimes accompanied by eye irritation or painful urination.

7. Bloodstream infection: In rare cases, bacteria enter the bloodstream, particularly in people with weakened immune systems

Source: Mayo Clinic, 2024

What should you do if you suspect a shigella infection?

If you think you have a shigella infection, these steps can help you recover and prevent spreading the bacteria to others:

• Wash your hands regularly: Use soap and water for at least 20 seconds, especially before eating, preparing food or sexual activity, and after using the toilet or changing nappies.

• Practise safe nappy changing: Dispose of used nappies in a covered bin, disinfect changing surfaces and wash both your hands and the child's hands afterwards.

• Avoid swallowing recreational water: Be careful when swimming in pools, lakes or ponds, as contaminated water can spread the bacteria.

• Follow food and water safety precautions: When travelling, drink safe water, eat properly prepared food and maintain good hand hygiene.

• Avoid sexual contact after infection: If you or your partner has shigellosis, wait at least two weeks after diarrhoea ends before having sex.

• Prevent spreading the infection when sick: Avoid preparing food for others, sharing food or swimming, and stay home from school or work while unwell. Certain jobs, particularly in healthcare, food service and childcare, may require additional clearance before returning.

Most mild shigella infections resolve without antibiotics, although more severe cases may require treatment.

Source: CDC, 2024; CDC, 2024

How can you test for a shigella infection?

A shigella infection is diagnosed through a medical assessment and a laboratory stool test. Because other conditions can cause similar symptoms, such as diarrhoea or bloody stools, a healthcare professional may collect a stool sample to check for the presence of shigella bacteria.

For broader digestive health insights, Homed-IQ offers convenient at-home stool tests, including the Microbiome Test. This test analyses the bacteria living in your gut and provides information about your gut microbiome. However, a microbiome test is not a diagnostic test for shigella and cannot confirm or rule out an active infection. If you suspect shigellosis, contact your GP for appropriate testing and advice.

Key takeaways about shigella infections

Shigella is a highly contagious bacterium that causes an intestinal infection called shigellosis. Common symptoms include diarrhoea, stomach cramps, fever and nausea, which usually resolve within five to seven days. The infection spreads through contaminated hands or surfaces, food, water or sexual contact involving exposure to infected stool. Although most people recover without complications, young children, older adults and people with weakened immune systems are at greater risk of serious illness. Good hygiene and avoiding close contact that could spread the bacteria can help prevent transmission. If you experience severe or persistent symptoms, particularly bloody diarrhoea, contact your GP for appropriate testing and treatment.