Overview
Shigella infection (shigellosis) is a highly contagious bacterial infection that primarily targets the intestine, causing severe diarrhoea, fever, stomach pain and an urgent need to pass stool even when the bowels are empty.
The infection spreads through direct contact with contaminated food and water and person-to-person interaction in unsanitary conditions. Symptoms usually start 1–2 days after exposure and can last up to a week or more. In some cases, bowel habits may not return to normal for several months.
Children under 5 and immunocompromised individuals are particularly susceptible to severe symptoms and complications.
Shigella can cause complications like bacteremia (the presence of bacteria in the bloodstream), seizures in young children, hemolytic uremic syndrome (HUS), a severe condition that results in the damaging of blood cells and can lead to kidney failure, and reactive arthritis, a painful form of inflammatory arthritis that develops in reaction to an infection in another part of the body.
Effective hygiene practices, consumption of safe food and water and vigilance when it comes to sanitation are crucial in preventing shigellosis. Treatment primarily involves hydration and rest, with antibiotics prescribed in severe cases. Public health efforts should include educating the general population, and at-risk groups in particular, on preventing transmission and managing symptoms.
Transmission
Shigella spreads through contaminated food and water and direct person-to-person contact in unsanitary conditions.
A very small number of shigella bacteria can cause an infection, making shigellosis highly contagious. Individuals who are infected can continue to transmit the bacteria to others for several weeks after symptoms such as diarrhoea have ceased.
Common routes of infection:
Hand-to-mouth transmission: Bacteria can be transferred from the hands to the mouth when contaminated surfaces in shared bathroom facilities, on utensils, water containers and communal toys, and in public changing areas such as those used for washing and cleaning children, are touched. Infection can also occur when changing the soiled clothes of an infected child, caring for someone with shigella and cleaning shared sanitation facilities after they have been used.
Contaminated food: Consuming food that has been prepared by someone infected with shigella.
Contaminated water: Ingesting water or drinking from sources contaminated with sewage such as unprotected wells and floodwaters.
Symptoms
Most people infected with shigella experience diarrhoea, which can be bloody and last more than three days, fever and stomach pain. There is often a feeling of needing to pass stool even when the bowels are empty, suggesting severe irritation and inflammation of the intestines.
Symptoms typically begin 1–2 days after infection and can last for about a week. In certain cases, it may take several months for bowel habits (frequency and consistency of stool) to return to normal.
Signs such as persistent diarrhoea, fever and stomach pain require prompt medical attention, especially if symptoms include bloody diarrhoea or severe discomfort that lasts beyond three days.
To manage symptoms effectively, and prevent serious complications such as dehydration, it is essential to consult health care workers immediately if symptoms develop, particularly in vulnerable populations like children and the elderly.
Vulnerable groups:
Children under 5: Young children, particularly those under 5 years of age, are most susceptible to shigellosis. Outbreaks can spread rapidly within tightly knit communities living in makeshift accommodation.
Immunocompromised individuals: People with weakened immune systems, whether due to conditions like HIV or treatments such as chemotherapy, may experience severe infections that can lead to life-threatening complications like bacteremia.
Treatment and management
Initial antibiotic treatment: In resource-limited settings where laboratory testing is not readily available, health care workers should rely on their observation of symptoms and knowledge of disease spread in the community when making decisions on treatment and outbreak management.
Consider initial antibiotic treatment in cases involving acute bloody diarrhoea and immunocompromised patients. Most individuals with shigella infection typically recover without antibiotics within 5 to 7 days.
For mild shigellosis, supportive care, such as adequate fluid intake and rest, is often sufficient.
Medications that slow intestinal movement, such as loperamide (Imodium) and diphenoxylate with atropine (Lomotil), should be avoided as they can interfere with the natural bacteria elimination process. In resource-limited settings where over-the-counter medications are not available, a focus on maintaining hydration and hygiene, ensuring rest and the use of local resources to create oral rehydration solutions can help manage symptoms effectively.
Preventing antimicrobial resistance: To combat the development and spread of resistant shigella strains, responsible antibiotic use is essential. Take antibiotics only when prescribed and precisely follow the treatment regimen, as directed by a health care provider.
Supportive care:
Hydration and rehydration: Ensure continuous hydration to combat the effects of diarrhoea. Prepare oral rehydration solutions using clean water, sugar and salt. The solution helps replenish fluids and electrolytes lost during bouts of diarrhoea.
Zinc supplements: Consider zinc supplements for children aged 6 months to 5 years.
Complications: Monitor for complications such as hypokalaemia (low potassium levels), hyponatremia (low sodium levels), hypoglycaemia (low blood sugar), seizures (due electrolyte imbalances) and encephalopathy (brain dysfunction due to toxins or infection). Long-term complications include persistent diarrhoea and prolonged malnutrition which may cause stunting and wasting in children.
Hemolytic-uremic syndrome (HUS): A rare but severe complication of shigella infection, HUS destroys red blood cells, leading to kidney failure, and is a notable risk in cases involving Shiga-toxin-producing shigella, primarily in young children.
Prevention
Hygiene in resource-limited settings:
If sinks are not available in patient care areas, Veronica buckets (portable handwashing stations) can be installed to provide water for hand hygiene close to the point of care. Alternatively, a handwashing basin, soap and a jug of clean water may be placed on a trolley used for ward rounds to encourage handwashing as often as needed between patient contacts.
When soap and clean water and alcohol-based handrub are unavailable, the following options can be considered:
Sodium hypochlorite added to water to achieve an end formulation of 0.05% sodium hypochlorite, for temporary use in dispenser containers for hand hygiene.
Note that sodium hypochlorite solution becomes inactive when exposed to air and organic materials. If this method is used during supply shortages it is recommended the solution be prepared in small batches daily and dispensed from closed containers.
Sodium hypochlorite can be added to water with a high saline content (seawater), as long as an end formulation of 0.05% sodium hypochlorite is achieved. Sources such as rainwater can also be considered.
Hand hygiene products that have antimicrobial properties such as waterless no-rinse hand soaps.
Hygiene practices: Maintain cleanliness to prevent infection. Regularly clean surfaces and practice good food hygiene.
Food and water safety: Boil or treat water and thoroughly cook food to kill bacteria. In resource-limited settings, use any available methods to purify water, including bringing it to a rolling boil for at least a minute.
Stay safe while on the move: Carry soap during travel or in transient living situations to maintain hygiene.
Prioritizing at-risk groups: Focus on securing preventive measures and medical support for individuals with compromised immune systems, such as those with chronic diseases, the elderly and young children, as they are more susceptible to severe complications. Early intervention and regular health monitoring are crucial to manage symptoms effectively and prevent disease progression.
Sanitation options for the safe disposal of human waste (excreta management) in resource-limited settings:
Target a maximum of 100 users per toilet.
Where there is a risk of overcrowding and limited availability of sanitation facilities, clearly mark places for safe excreta disposal or, if buckets are used, the location of manholes. Deliver key messages on handwashing after touching excreta.
Establish deep trench latrines and locate them away from water sources. Toilets should be accessible, and their placement take into account the safety and security of users (e.g. children and older people must be able to use them and they should be equipped with safety features such as locks and lighting to minimize the risk of gender-based violence).
Pay community workers to clean and clear standing wastewater around shelters.
Where hospitals and schools are being used as shelters and are overcrowded, if space is available increase the number of toilets or latrines outside the shelter.
Make saline water available for anal washing and separate it from water used for flushing. Label everything clearly.
Provide supplies (biodegradable plastic bags, cleaning materials and soap) and ensure maintenance and collection services for plastic bag toilet systems and bucket or elevated latrines when there are no safer sanitation options.
Community engagement and health care coordination
Develop community awareness about shigella, focusing on symptoms, transmission and effective prevention techniques. Share knowledge on food and water safety and maintaining good hygiene practices.
Education improving understanding and awareness of shigella should target all age groups, and vulnerable populations in particular.
Sources
Guidelines for the control of shigellosis, including epidemics due to shigella dysenteriae type 1. Geneva: World Health Organization; 2005 (https://www.who.int/publications/i/item/9241592330).
Infection prevention and control and water, sanitation and hygiene measures in health-care settings and shelters/congregate settings in Gaza: technical note. Geneva: World Health Organization and United Nations Children’s Fund; 2024 (https://www.unicef.org/sop/media/3681/file/Infection%20prevention%20%20and%20control%20and%20water,%20%20sanitation%20and%20hygiene%20%20measures%20in%20health-care%20%20settings%20and%20shelters%20congregate%20settings%20in%20Gaza.pdf).
Shigella – Shigellosis. Atlanta: Centers for Disease Control and Prevention; 2024 (https://www.cdc.gov/shigella/about/index.html).