Chagas (pronounced SHA-gus) disease is named after the Brazilian physician Carlos Chagas, who discovered it in 1909. It is caused by the parasite Trypanosoma cruzi, which is transmitted to animals and people by insect vectors that are found only in the Americas (mainly, in rural areas of Latin America where poverty is widespread). Chagas disease (T. cruzi infection) is also referred to as American trypanosomiasis.

Chagas' disease currently affects 16'18 million people, with some 100 million (25% of the Latin American population) at risk of acquiring the disease, killing around 50,000 people annually. Chronic Chagas' disease remains a major health problem in many Latin American countries, despite the effectiveness of hygienic and preventive measures, such as eliminating the transmitting insects, which have reduced to zero new infections in at least two countries of the region. With increased population movements, however, the possibility of transmission by blood transfusion has become more substantial in the United States. Approximately 500,000 infected people live in the USA, which is likely the result of immigration from Latin American countries.

Chagas disease is caused by Trypanosoma cruzi, a parasite related to the African trypanosome that causes sleeping sickness. It is spread by reduvid bugs and is one of the major health problems in South America, where 20 million people are infected. Due to immigration, about 500,000 people in the United States are believed to be infected. Risk factors for Chagas disease include living in Central or South America, poverty, living in a hut where the reduvid bugs live in the walls, and receiving a blood transfusion from a person who carries the parasite but does not have active Chagas disease.

Chagas disease is usually spread by the feces of the reduviid bug, an insect that infests mud, adobe, or thatch houses. People get infected when they unknowingly rub bug feces into their eyes or mouth or into a bite wound. Infection can be also be transmitted by blood transfusions or organ transplants. An infected woman can pass the infection to her baby during pregnancy, at delivery, or while breastfeeding. Chagas disease can cause symptoms soon after infection, but many people do not become ill until many years later. Persons with weakened immune systems are at greatest risk of severe infections and complications.

The adult and nymphal stages of Triatominae can be infected by T cruzi sucking blood from infected mammals. In the intestinal tract of insects, the absorbed trypomastigotes undergo transformations into spheromastigotes and epimastigotes that divide by binary fission. Some epimastigotes migrate to the terminal part of the intestine and the malpighian tubules. By binding to the rectal epithelium, they are transformed into metacyclic trypomastigotes. The metacyclogenesis of T cruzi involves cyclic adenosine monophosphate (cAMP) and various factors contained in urine and the digestive tract of the insect. The infective forms of the parasite are then discharged with the feces and urine at the end of the blood meal. The complete intravectorial life cycle of T cruzi is achieved in 2-4 weeks.

reatment in the acute stage rapidly reduces parasitemia, shortens the clinical illness, and reduces risk of mortality but often does not eradicate the infection. Treatment of children and young adults with indeterminate infections has been recommended, but many are not cured. Treatment in the chronic stage is symptomatic. Chronic organ damage, which may be caused in part by host inflammatory responses, appears to be largely irreversible. Supportive measures include drugs for heart failure, pacemakers, antiarrhythmic drugs, cardiac transplantation, esophageal dilation, and GI tract surgery.