Carlos Justiniano Ribeiro Chagas, or Carlos Chagas (; July 9, 1879 – November 8, 1934), was a Brazilian sanitary physician, scientist, and bacteriologist who worked as a clinician and researcher. He discovered Chagas disease, also called American trypanosomiasis, in 1909, while he was working at the Oswaldo Cruz Institute in Rio de Janeiro. Chagas's work holds a unique place in the history of medicine. Working in primitive conditions, Chagas described in detail a previously-unknown infectious disease, its pathogen, vector (Triatominae), host, clinical manifestations, and epidemiology. Chagas was also the first to discover and illustrate the parasitic fungal genus Pneumocystis, which later became infamous for being linked to pneumocystis pneumonia in AIDS patients. Early life Chagas was the son of José Justiniano das Chagas, a coffee farmer from Minas Gerais, and Mariana Cândida Chagas, both of Portuguese descent. After his secondary studies at Itu, São Paulo and São João del Rei, he enrolled in the School of Mining Engineering at Ouro Preto, but changed to the Medical School of Rio de Janeiro in 1897, influenced by his uncle, who was a physician and owner of a hospital in that city. He graduated in 1902 and got his M.D. the following year with a thesis on the hematology of malaria, working at the new medical research institute created by noted physician, and later friend and colleague, Oswaldo Cruz (1872–1917). After a brief stint as a medical practitioner in the hinterlands, Chagas accepted a position in the port authority of Santos, São Paulo, with the mission of fighting the malaria epidemic, which was affecting its workers. There, he introduced an innovation, which consisted in using pyrethrum, an insecticide, to treat households, with surprising success. His published work on this method served as the basis of prevention of malaria all over the world, and was adopted by a service of the Ministry of Health in Brazil, which was established expressly for this purpose. Discovery of Chagas disease In 1906, Chagas returned to Rio de Janeiro and joined the Oswaldo Cruz Institute, where he remained working for the rest of his life. In 1909, he was sent by the institute to the small city of Lassance, near the São Francisco River, to combat a malaria outbreak among the workers of a new railroad to the city of Belém in the Amazon. He stayed there for the next two years, and soon was able to observe