Without treatment, parasitemia falls and any acute symptoms resolve over a period of about 8 weeks, and T. cruzi-infected persons progress from the acute phase to the chronic phase of Chagas disease.

Patients diagnosed in the U.S. will usually be in the chronic phase of the disease. Since most infections are acquired in endemic areas of Mexico, Central America, and South America, U.S. physicians will rarely see patients with acute Chagas disease.