 Chagas named the pathogenic parasite as Trypanosoma cruzi and later that year as <unk> cruzi , both honoring <unk> Cruz , the noted Brazilian physician and <unk> who successfully fought <unk> of yellow fever , smallpox , and <unk> plague in Rio de Janeiro and other cities in the beginning of the 20th century . Chagas was also the first to unknowingly discover and illustrate the parasitic fungal genus Pneumocystis , later <unk> linked to <unk> ( Pneumocystis pneumonia in AIDS victims ) . Confusion between the two pathogens ' life @-@ cycles led him to briefly recognize his genus <unk> , but following the description of Pneumocystis by others as an independent genus , Chagas returned to the use of the name Trypanosoma cruzi . 
