Dysentery

Dysentery is an infection of the intestines, specifically the colon, that causes inflammation and leads to bloody diarrhea. Historically called the bloody flux, it has been recognized as a disease since at least the time of Hippocrates. The condition usually clears up on its own within about a week, but staying hydrated—especially with oral rehydration solution—is important. For cases linked to travel in developing countries, antibiotics like azithromycin may be prescribed. Medications that slow diarrhea, such as loperamide, are not recommended alone but can be used alongside antibiotics.

The most common cause is bacteria from the genus *Shigella*, a form known as shigellosis. Another major cause is the amoeba *Entamoeba histolytica*, which leads to amoebiasis, or amoebic dysentery. Other triggers include certain chemicals, other bacteria, other protozoa, and parasitic worms. The infection spreads between people, often through food or water contaminated with feces due to poor sanitation. The underlying problem is inflammation of the intestine, especially the colon.

Symptoms usually appear one to three days after exposure and include mild abdominal pain and frequent loose stools or diarrhea. The severity varies: some people pass more than a liter of fluid per hour, while others have bloody diarrhea with extreme abdominal and rectal pain, plus a low-grade fever. Rapid weight loss and muscle aches can occur, but nausea and vomiting are rare. Temporary lactose intolerance may also develop. In severe cases, symptoms can include high fever, shock, and delirium.

Bacterial infections that cause bloody diarrhea are either invasive (damaging the intestinal lining directly) or toxogenic (secreting toxins that damage cells). The damage triggers an inflammatory immune response, leading to fever, painful muscle spasms in the intestines, swelling from fluid leaking out of capillaries, and further tissue harm from immune cells and cytokines. This can impair nutrient absorption, cause excessive water and mineral loss through stool, and, in severe cases, allow pathogens to enter the bloodstream. Anemia may result from blood loss.

Amoebic dysentery is caused by the amoeba *Entamoeba histolytica*, which is mostly found in tropical areas. When amoebae inside the bowel are ready to leave the body, they form a protective shell called a cyst, which is passed in feces. If hygiene is poor, these cysts can contaminate food and water. If another person consumes contaminated food or water, they can become infected. Proper treatment is crucial because untreated amoebiasis can lie dormant for years and later cause severe, potentially fatal complications. On rare occasions, the amoeba can enter the bloodstream and spread beyond the intestines, infecting organs like the liver, lungs, or brain.

*Shigella* causes about 165 million cases of diarrhea and 1.1 million deaths each year, nearly all in the developing world. In areas with poor sanitation, almost half of diarrhea cases are due to *Entamoeba histolytica*, which affects millions of people and causes more than 55,000 deaths annually. It is common in less developed parts of Central and South America, Africa, and Asia. Definitions of dysentery vary: the U.S. Centers for Disease Control and Prevention (CDC) defines it strictly as "diarrhea with visible blood," while other definitions are broader. Prevention includes hand washing and food safety measures when traveling to high-risk countries.