Beriberi outbreaks in the São João de Deus Asylum, 1897-1904, are presented, focusing on studies by legist physician Nina Rodrigues. The goals were: to trace the steps of the original investigation of an unknown disease; to understand the purpose of excluding mentally ills in an asylum institution. Methodology encompassed occurence narration and qualitative analytical procedures for the documental interpretation of voluntary and involuntary testimonies, combined with statistical treatment of measurable data. Frequent and progressive outbreaks of beriberi have caused two-thirds of the asylum deaths in 1904. The research method included domiciliary visits and interviews with dwellers in the asylum surroundings. Beriberi occurence was frequent among the insane and practically inexistent among the asylum staff, who presented close and long lasting contact with the ills. Nina Rodrigues refuted the declining miasmatic conception which emphasized external conditions, the emergent conception of contagion, and raised the hypothesis of a carential etiology for beriberi. Nina Rodrigues' study is a good historical example of "epidemiological reasoning," with question formulation, building of data bulk guided by working hypothesis, obtained by means of simple and efficient techniques.
history of epidemiology; history of psychiatry; psychiatric epidemiology; beriberi