Epidemiological and ecological characteristics of past dengue virus infection in Santa Clara, Peru

To determine risk factors associated with dengue (DEN) virus infection amon g residents of Santa Clara, Peru, a rural Amazonian village near Iquitos, a cross-sectional serological, epidemiological and environmental survey was conducted. Demographic, social and behavioural information was obtained by standardized questionnaire from 1225 Santa Clara residents (61.3%,) aged 5 years or older. Additional data were obtained on the environmental variable s and immature mosquito species and abundance surrounding each household (n = 248). Sera that had been collected previously by the Peruvian Ministry o f Health from residents were tested by an enzyme-linked immunosorbent assay (ELISA) for DEN virus IgG antibody. Antibody identity was verified as DEN by plaque reduction neutralization test. Data on individuals were analysed hy univariate and multivariable methods, and independent sample t-tests. Sp atial clustering was evaluated by comparing distances among DEN positive ho useholds. Overall, antibody prevalence was 29.4% and more than doubled from the youngest to the oldest age groups, but did not differ by sex. Curiousl y, length of residence in Santa Clara was negatively associated with DEN vi rus antibodies. More frequent travel to Iquitos was positively associated w ith seroprevalence. Residents who obtained water from a river source rather than a local well also had significantly higher antibody prevalence. None of the environmental variables measured at each household corresponded to t he patterns of antibody distribution. OF the larval mosquitoes found around residences, all were determined to be species other than Aedes. No evidenc e of spatial autocorrelation among antibody-positive households was detecte d. These results strongly suggested that recent DEN virus transmission did not occur in the village and that most infections of residents of this rura l village were acquired while visiting the city of Iquitos.