[Sanitary battles and scientific clashes: Emilio Ribas and yellow fever in Sao Paulo].

Emilio Ribas, an administrative physician and sanitarian from Sao Paulo, was an advocate of the microbiological conception during the long period when he directed the Servico Sanitario de Sao Paulo (1898-1917). This article offers a brief analysis of his stance in the flight against yellow fever during the early 20th century, considered a highlight of his career. The scientists and professionals linked to this sanitary agency in Sao Paulo found themselves in a tense, unstable work environment, where experimental proof played an important role in corroborating new medical-sanitary conceptions and practices. The article takes a close look at the medical experiments on yellow fever directed by Emilio Ribas and conducted at Sao Paulo's Hospital de Isolamento in 1902-03. It examines these same studies in an effort to better understand how the significance of yellow fever was transformed and to explore its implications regarding the history of public health in Sao Paulo.