Chagas' disease, disease of South and Central America caused by the parasite Trypanosoma cruzi. It usually affects children and young adults and is transmitted by the feces of infected insects, typically the assassin bug. Most of those infected have mild symptoms, such as fever and swelling and redness around the eyes, but from 10% to 30% develop chronic disease that may result in serious or fatal inflammation of the brain and heart tissues; persons with the disease also have an increased risk for stroke as they age as a result of heart problems. There is no vaccine and no satisfactory treatment. The incidence of Chagas' disease in the United States has increased since the 1970s, possibly because of increased immigration from Mexico and Central America, where the incidence is very high. In immunosuppressed patients (see AIDS) Chagas' disease can form a mass in the cranial cavity that mimics a tumor, presumably because the lymphocytes that guard against the parasite are the same that are depleted by the AIDS virus. See also trypanosome.