Dysentery is one of the oldest known gastrointestinal disorders. The English word dysentery comes from two Greek words meaning “ill” or “bad” and “intestine.” Dysentery was described as early as the Peloponnesian War in the fifth century BCE. Epidemics of dysentery were frequent occurrences aboard sailing vessels and in army camps, walled cities, and other places in the ancient world where large groups of people lived together in close quarters with poor sanitation. As late as the eighteenth and nineteenth centuries, sailors and soldiers were more likely to die from what they called the bloody flux than from injuries received in battle. King Henry V of England died of dysentery in 1492. A Vietnamese revolutionary who fought against French colonial forces in Vietnam died of dysentery in 1896 while the French army surrounded the Vietnamese forces. However, it was not until 1897 that the bacillus (rod-shaped bacterium) was identified as the cause of one major type of dysentery. Thereafter, researchers investigated infections of the digestive tract wherever such illnesses occurred, and many more direct causes of dysentery, including various bacteria, viruses, parasitic worms, and protozoa, were identified.

In the twenty-first century, outbreaks of dysentery continue to occur and, though they are rare, can still be deadly. In 2013, Shigella was responsible for the deaths of 34,000 children under age five, and as of 2018 amebiasis was still reported to infect over 50 million individuals each year, resulting in death for nearly 50,000. In 2016, a large outbreak of shigellosis, a type of bacillary dysentery caused by Shigella occurred in Michigan, the largest outbreak since 1988. The bacteriophages (viruses that infect bacteria) that caused the outbreak were from environmental water sources. The World Health Organization (WHO) continues to search for a vaccine against Shigella. However, vaccine development has not been widely supported since major outbreaks of dysentery are infrequent and unpredictable, whereas, in contrast, many highly prevalent diseases command the attention of researchers and receive the necessary funding for studies. Meanwhile, the WHO maintains surveillance for outbreaks and urges biotechnology companies to continue on the path of vaccine development.


Dysentery is a common but potentially serious inflammatory disorder of the digestive tract characterized by acute bloody diarrhea. It occurs throughout the world and is caused by a number of infectious agents, ranging from viruses and bacteria to protozoa and parasitic worms; it may also result from drinking contaminated water or through chemical irritation of the intestines. The difference between dysentery and common diarrhea is that dysentery is an inflammatory disease characterized by acute diarrhea with stool containing blood and mucus, whereas common diarrhea is essentially characterized by only loose, watery stool.

The term dysentery is used in different ways by clinicians and researchers and even international organizations such as the WHO and Centers for Disease Control and Prevention. Although some medical professionals use the term in a broad sense to group all forms of intestinal inflammation with acute diarrhea, other professionals use the term to refer only to bacillary dysentery caused by Shigella species (shigellosis) and amebic dysentery, and all other forms of diarrheal disease fall under the term diarrhea. Still others specify the causal agent of acute diarrheal disease, speaking of schistosomiasis, a disease caused by a parasitic worm, as bilharzial dysentery or referring to acute diarrhea caused by viruses as viral dysentery or viral gastroenteritis.

Risk factors

Poor sanitation, contaminated water supplies, and crowded living conditions are the greatest risk factors for developing dysentery. In the modern world, dysentery is most likely to affect people in less developed countries and travelers who visit these areas. According to the CDC, most cases of dysentery in the United States occur in immigrants from developing countries and in persons who live in crowded inner-city housing with poor sanitation. Other groups at increased risk of contracting dysentery or developing severe symptoms are military personnel stationed in developing countries, frequent travelers, young children (especially those in daycare centers), people in nursing homes, pregnant women, and men who have sex with men.

Dysentery is particularly common after natural disasters such as earthquakes, tsunamis, floods, or hurricanes during which water supplies are contaminated, sewage treatment is disrupted, and people are forced to live in crowded temporary shelters. These disasters promote the spread of dysentery through contact with human and animal feces in soil and water, contaminated food, and unsanitary living facilities.


Shigellosis, or infection by any of the species of Shigella, occurs worldwide wherever and whenever natural or manmade disasters occur such as earthquakes and floods, war, and crowded, unsanitary living conditions. The CDC estimates that 500,000 cases of dysentery are caused by various species of Shigella in the United States each year. The most common cause (about 85% of cases) in the United States is S. sonnei, followed by S. Flexneri; S. boydii and S. dysenteriae are rare in the United States. Worldwide, Shigellosis affects 165 million individuals and causes 700,000 deaths annually. The most common species worldwide are S. dysenteriae and S. boydii, which are found primarily in developing countries. Acute diarrheal disease stemming from S. dysenteriae can be particularly deadly. Shigellosis occurs more frequently in children aged six months to five years. Gender differences are not noted in adults.

Entamoeba histolytica, the cause of amoebic dysentery, is found worldwide but is most prevalent in developing countries where water and food are often contaminated with human feces and where, according to CDC surveillance reports, up to 50% of the population can be infected. Internationally, E. histolytica is second only to the organism that causes malaria as a protozoal cause of death. It is estimated to account for 40–50 million cases of dysentery each year and 40,000–100,000 deaths.

In the United States, amebic dysentery is uncommon. Most cases occur in recent immigrants from heavily infected (endemic) areas or travelers returning from those areas. Instead, Giardia intestinalis (previously known as G. lamblia) is the most common parasite found in stool samples in the United States. It causes dysentery primarily in children under age three. Infection usually occurs through contaminated water. Most cases are reported in mountainous areas in the West. About 23,000 cases are reported to the CDC each year, although the infection rate is likely much higher since many cases go unreported and untreated.

Giardiasis is a major diarrheal disease found globally and waterborne and foodborne outbreaks are common wherever people gather such as daycare facilities and institutional settings. G. intestinalis is common worldwide in both tropical and temperate regions, and, in the United States, it is the most common intestinal parasite. The organism is found in up to 80% of raw water in lakes, streams, and ponds, and even in up to 15% of filtered water. From 2%–5% of the population in the developed world is infected. The rate is much higher in developing countries with a reported rate of over 70% in Nepal. Infection occurs more often in children than in adults and is a cause of chronic diarrhea and growth retardation in developing countries.

Schistosomiasis, also called bilharzia or bilharzial dysentery, is a widespread tropical disease caused by parasitic flukes (trematode worms) of the genus Schistosoma. Although the disease is rare in the United States, travelers to countries where it is endemic may contract it. The World Health Organization (WHO) estimates that about 200 million people around the world carry the parasite in their bodies, and about 20 million develop severe infection.

Worldwide, viral dysentery (also called viral gastroenteritis) is the leading cause of infant death, accounting for 600,000–875,000 deaths per year. About 3.5 million cases of viral dysentery in infants are reported in the United States each year and about 23 million cases each year in adults. The CDC estimates that viruses are responsible for 9.2 million cases of dysentery associated with food poisoning in the United States annually, many caused by foods imported from Asian sources, with fish products among the most common.

Causes and symptoms

Diarrhea and acute diarrheal disease is described by the CDC as a common illness and a global killer. Symptoms are fairly consistent regardless of the cause but can be more severe when caused by certain organisms and in certain individuals, particularly those whose immune system function is compromised by age (infants and older adults), HIV/AIDS, or chronic disease.


The most common types of dysentery and their causal agents are:


Compared to the characteristic bloody diarrhea, abdominal cramps, and pain of dysentery, symptom profiles of forms of dysentery may vary somewhat in onset, duration, presence of fever, or complications, as follows:


Patient history and physical examination

Identifying a specific causal source for acute diarrhea is not possible through physical examination alone, although the presence or absence of fever and signs of dehydration from loss of fluid may help to narrow the diagnostic possibilities. Evaluating the patient for fatigue, drowsiness, dryness of the mucous membranes lining the mouth, low blood pressure, loss of normal skin tone, and rapid heartbeat (above 100 beats per minute) may indicate that the patient is dehydrated and needs immediate rehydration. The patient's age and recent history usually provide better clues about potential causes for the acute diarrhea. The doctor may ask about the household water supply and food preparation habits, recent contact with or employment in a nursing home or daycare center, recent visits to tropical countries, and similar questions. The doctor will also need to know when the patient first noticed the symptoms and how the patient may have progressed since then.

Laboratory tests

Microscopic examination of a stool sample is the most common laboratory test to determine the cause of dysentery. The patient will usually be asked to avoid using over-the-counter antacids or antidiarrheal medications until the sample has been collected, as these preparations can interfere with the test results. The organisms that cause cryptosporidiosis, bacillary dysentery, amebic dysentery, and giardiasis can be seen under a microscope. The eggs produced by parasitic worms can also be viewed, although they may not be present in all stool samples examined. Repeated stool examination, a sample of mucus from the intestinal lining obtained through proctoscopic examination, or a biopsy (removal and microscopic examination) of tissue scraped from the mucus membrane inside the patient's colon may be necessary to identify the causative organism and extent of damage to the intestines. Antigen testing of a stool sample can be used to diagnose a rotavirus infection as well as parasitic worm infestations.

The doctor will usually order a blood sample to be drawn for a complete blood count to confirm infection, measurement of electrolyte levels to check for dehydration, and kidney and liver function tests that may be altered by infestation with certain organisms.

Imaging studies

Imaging studies (usually CT scans, x rays, or ultrasound) may be performed in patients with suspected amebic dysentery or schistosomiasis to determine whether the liver or lungs have been affected. Ultrasound or magnetic resonance imaging (MRI) may be done to examine liver, intestinal, or bladder tissue in more detail and search for eggs produced by worms.


Fluid replacement (rehydration) is begun immediately if the patient shows signs of dehydration. The most common treatment is administration of oral rehydration fluid (e.g., the WHO formula, Pedialyte, or Infalyte) containing a precise amount of sodium (salt) and a smaller amount of glucose (sugar) to replace fluid and electrolytes (sodium, potassium, chloride) lost through acute diarrhea.

Medications, including antibiotics, are the primary form of treatment for most types of dysentery, including the following:


Surgery is rarely necessary in treating dysentery but may be required in cases of fulminant colitis if the patient's colon has perforated. Patients with liver abscesses resulting from amebic dysentery may also require emergency surgery if the abscess ruptures. In some cases, laparoscopic exploratory surgery may be performed to determine whether severe abdominal pain is caused by schistosomiasis, amebic dysentery, or appendicitis.

Alternative treatments

A number of alternative or complementary treatments for dysentery are available, most of which are derived from plants that have been used by native healers for centuries. Because dysentery was known to ancient civilizations as well as modern societies, such alternative systems as Ayurvedic medicine and traditional Chinese medicine (TCM) developed treatments for it.

Ayurvedic medicine

Ayurvedic practitioners recommend specific fruits and herbs to treat dysentery, including cumin seed, bael fruit (Aegle marmelos, also known as Bengal quince), and arjuna (Terminalia arjuna) bark. Ayurvedic medicine also recommends dietary supplements known as Isabbael, Lashunadi Bati, and Bhuwaneshar Ras. To rehydrate the body, adult patients may be given a beverage combining slippery elm water and barley, at least a pint per day.

Traditional Chinese Medicine
A type of drug or herbal preparation given to destroy parasitic worms or expel them from the body.
A rod-shaped bacterium. One common type of dysentery is called bacillary dysentery because it is caused by the bacillus Shigella.
A virus that infects bacteria and can be a cause of dysentery. Also called simply phages.
A disease, pathogen, or type of infection occurring naturally and consistently in a particular area.
A type of harmful protein released by bacteria and other disease agents that affects the tissues lining the intestines.
An outbreak of disease in which the number of cases exceeds the usual (endemic) or typical number of cases.
Occurring or flaring up suddenly and with great severity. A potentially fatal complication of amebic dysentery is an inflammation of the colon known as fulminant colitis.
Food supplements containing live bacteria or other microbes intended to improve or restore the normal balance of microorganisms in the digestive tract.
A tubular fiberoptic instrument with a light source and a tiny camera used to examine the inside of the rectumand transmit images to a monitor for viewing.
Protozoan (plural, protozoa)—
A one-celled organism that is among the simplest forms of animal life. Amoebic dysentery is caused by a protozoan.
Reiter syndrome—
A group of symptoms, including arthritis symptoms, inflammation of the urethra, and conjunctivitis, which develops as a late complication of infection with Shigella flexneri. The syndrome was first described by German doctor Hans Reiter in 1918.
A characteristic of bacillary dysentery that involves ineffective spasms of the rectum or bladder accompanied by the desire to evacuate stool or pass urine but inability to do so.
The active feeding stage of a protozoal parasite that is distinct from its encysted stage.
Other plant-based remedies

The roots of Geranium mexicanum, a plant that produces a sap used in conventional Mexican medical care to treat coughs or diarrhea, contains compounds shown to be active against both G. and E. histolytica. The effectiveness of African mistletoe (Tapinanthus dodoneifolius), a traditional remedy for dysentery among the Hausa and Fulani tribes of Nigeria, has also been noted by plant biologists in Africa.

Dietary supplements

The CDC reports that in many instances the administration of zinc at twice the recommended daily dietary allowance along with rehydration therapy and antibiotic therapy significantly shortens the duration and severity of dysentery in children.


At least ten different homeopathic remedies are used to treat diarrhea. Contemporary homeopathic physicians distinguish between diarrhea that can be safely treated at home with such homeopathic remedies as Podophyllum, Veratrum album, Bryonia, and Arsenicum and diarrhea that indicates dysentery and should be referred to a physician. Signs of dehydration (loss of normal skin texture, dry mouth, sunken eyes), severe abdominal pain, blood in the stool, and unrelieved vomiting are all indications that mainstream medical care is required.

Public health role and response

Public health measures to control outbreaks of dysentery include the following:

http://www.cdc.gov/travel/ ) provides up-to-date travel information.
  • Instructing restaurant workers and other food handlers about proper methods of hand washing, food storage, and food preparation.
  • Instructing workers in daycare centers and nursing homes about the proper methods for changing, cleaning, and disposing of soiled diapers and bedding.
  • Inspecting wells, other sources of drinking water, and swimming pools for evidence of fecal contamination.
  • Testing public water sources such as lakes, ponds, and public pools for the presence of contaminants and infectious agents.
  • Prognosis

    Most adults in developed countries recover completely from an episode of dysentery. Children are at greater risk of becoming dehydrated, however; bacillary dysentery in particular can lead to a child's death from dehydration in as little as 12–24 hours. Older adults, particularly institutionalized adults, are also at greater risk of infection leading to acute diarrhea, related dehydration, and life-threatening complications.



    Personal precautions

    Individuals can lower their risk of contracting dysentery by the following measures:

    See also Centers for Disease Control and Provention ; Drinking-water supply ; Parasites ; Traveler's health ; Viruses ; Water quality .



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    Centers for Disease Control and Prevention (CDC), 1600 Clifton Rd., Atlanta, GA, 30329-4027, (404) 639-3534, (800) 232-4636), cdcinfo@cdc.gov, http://www.cdc.gov .

    Infectious Diseases Society of America (IDSA), 1300 Wilson Blvd., Ste. 300, Arlington, VA, 22209, (703) 299-0200, Fax: (703) 299-0204, info@idsociety.org, http://www.idsociety.org .

    World Health Organization, Avenue Appia 20, 1211 Geneva 27, Switzerland, 41 22 791 21 11, Fax: 41 22 791 31 11, info@who.int, http://www.who.int .

    Rebecca Frey, PhD
    Revised by L. Lee Culvert

      This information is not a tool for self-diagnosis or a substitute for professional care.