Variola minor in Bragança Paulista County, 1956: overall description of the epidemic and of its study.

An overall description of the epidemic of variola minor (alastrim) affecting Bragança Paulista County (Brazil) in 1956 is given. A total of 484 cases were recorded for 210 households, one hotel and one boarding school. At least 95 per cent of the households with cases of the disease in the capital city were surveyed and 90 per cent of the households in the rural districts. An orphanage, an old folk's home, the County jail and 10 schools operating in the capital city and some other social groups without cases were also surveyed, as well as 125 households without cases but with one or more contacts with the disease. An overall attack rate of 1924 cases, 267 cases and 781 cases per 100,000 inhabitants was obtained, respectively, for the capital city, the rural environment and the whole County. Clinical, epidemiological, serological and environmental surveys were conducted. Evidence on identification of the epidemic disease is presented. Study of the epidemic was made at these levels: the disease itself (frequency and severity); the disease in the individual (association of characteristics of persons with occurrence and clinical severity of variola minor); the disease in social units (occurrence and spread in households and school classes); the disease in small communities (occurrence and spread in housing projects, city blocks and farms); the disease in two large communities with contrasting socio-economic characteristics (the capital city and the rural environment); and the disease in the County as a whole.