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OBJECTIVE: To determine the seroprevalence of dengue fever serotypes in three sanitary districts in the city of Belo Horizonte and investigate the association of seroprevalence with contextual and individual variables. METHOD: The survey was conducted in the sanitary districts of Venda Nova, Leste and Centro-Oeste between June 2006 and March 2007. All residents aged 1 year or older were eligible for the study. Participants answered a questionnaire and had a 5 mL blood sample collected to determine the presence of anti-dengue types 1, 2, and 3 virus antibodies by seroneutralization. The questionnaire covered demographic aspects, socioeconomic status, physical characteristics of the home, residential mobility between cities, previous history of signs and symptoms associated with dengue fever, and knowledge concerning dengue fever prevention measures, among others. RESULTS: Seroprevalence was 11.9% (95%CI: 9.7-14.6) among the 709 individuals included in the study, and it was not associated with sex, age, family income, and having moved to another town in the past 10 years. Seropositivity was associated with type of construction (apartment or house/shanty, with apartment being a protection factor) and with an elevated health vulnerability index where the dwelling was located. CONCLUSIONS: In this study, seroprevalence was lower than in previous studies carried out in mid-size and large Brazilian cities. This suggests that Belo Horizonte has employed efficient control measures. However, heterogeneity within the city was observed in terms of dengue fever transmission, which was largely associated with contextual indicators of vulnerability. The number of susceptibles is still high, and the control of dengue fever remains a difficult public health issue. [ABSTRACT FROM AUTHOR]