Careful consideration of the patient’s history to identify possible risks for infection may be helpful. Acute infections can be diagnosed by the identification of trypomastigotes in blood by microscopy. During the chronic phase, circulating parasite levels decrease rapidly within a few months and are undetectable. 
Chronic Chagas disease is made by serologic tests for antibodies to the parasite. A single test is not sufficiently sensitive and specific to make the diagnosis. For this reason, the standard approach is to apply two or more tests that use different techniques and that detect antibodies to different antigens. Commonly used techniques include enzyme-linked immunosorbent assay (ELISA) and immunofluorescent antibody test (IFA).
Chagas disease diagnostic criteria
Chagas disease laboratory findings
Measles diagnostic criteria
Chagas disease physical examination
Leprosy diagnostic criteria
Enterovirus 68 differential diagnosis
Babesiosis physical examination
Rabies diagnostic criteria