Malaria is a widespread cause of serious infection in Asia and Africa and may be acquired by travelers or military personnel. The standard diagnostic test is still the examination of thick and thin peripheral blood smears. It has been recommended that smears be collected just after episodes of chills and also 10 hours later. A more recent method is the QBC malaria test, based on a special tube containing patient blood and acridine orange dye, high-speed centrifugation, and examination under fluorescent light for malarial parasites that are collected just below or in the buffy coat layer.

Babesiosis is an uncommon red blood cell infestation in the United States originally found on Nantucket island in New England. The organism responsible is a protozoan from the genus Babesia, which infects several species of animals (especially rodents) and has a tick vector. In humans, the infection is either asymptomatic or is manifested by a mild or moderate febrile illness, usually self-limited, which may be accompanied by mild hemolytic anemia. Splenectomized persons, however, develop severe illness. Diagnosis necessitates the same tests used in malaria.