Seroprevalence and risk factors for dengue infection in socio-economically distinct areas of Recife, Brazil.

Brazil currently accounts for the majority of dengue cases reported in the Americas, with co-circulation of DENV 1-3. Striking variation in the epidemiological pattern of infection within cities has been observed. Therefore, investigation of dengue transmission in small areas is important to formulate control strategies. A population-based household survey was performed in three diverse socio-economic and environmental areas of Recife, a large urban center of Brazil, between 2005 and 2006. Dengue serostatus and individual- and household-level risk factors for infection were collected in residents aged between 5 and 64 years. A total of 2833 individuals were examined, and their residences were geo-referenced. Anti-dengue IgG antibodies were measured using commercial ELISA. The dengue seroprevalence and the force of infection were estimated in each area. Individual and household variables associated with seropositivity were assessed by multilevel models for each area. A spatial analysis was conducted to identify risk gradients of dengue seropositivity using Generalized Additive Models (GAM). The dengue seroprevalence was 91.1%, 87.4% 74.3%, respectively, in the deprived, intermediate and high socio-economic areas, inversely related to their socio-economic status. In the deprived area, 59% of children had already been exposed to dengue virus by the age of 5 years and the estimated force of infection was three times higher than that in the privileged area. The risk of infection increased with age in the three areas. Not commuting away from the area was a risk factor for seropositivity in the deprived area (OR=2.26; 95% CI: 1.18-4.30). Number of persons per room was a risk factor for seropositivity in the intermediate (OR=3.00; 95% CI: 3.21-7.37) and privileged areas (OR=1.81; 95% CI: 1.07-3.04). Living in a house, as opposed to an apartment, was a risk factor for seropositivity in the privileged area (OR=3.62; 95% CI: 2.43-5.41). The main difference between the privileged and other areas could be attributed to the much larger proportion of apartment dwellers. Intensive vector control, surveillance and community education should be considered in deprived urban areas where a high proportion of children are infected by an early age.