Risk factors for dengue infection during an outbreak in Yanes, Puerto Rico in 1991.

In November 1991, during a five-month dengue outbreak, we performed epidemiologic and serologic surveys linked to an earlier entomologic study in a community of 425 houses in Yanes (Florida), Puerto Rico. We obtained a household response rate of 95% (98 of 103) and blood samples from 84% (345 of 410) of the participants. Dengue incidence, as volunteered by the respondents, was 5% (21 of 410), but serologic diagnosis (immunoglobulin M and IgG-enzyme-linked immunosorbent assays [ELISA]) indicated a recent infection rate of 18% (59 of 331). The presence of anti-dengue antibodies was detected in 277 (84%) of 331 persons tested. In our final sample of 65 households and 112 persons, we analyzed (by univariate and multivariate logistic regression methods) the association of 12 entomologic, environmental, and behavioral variables with the proportion of household members with laboratory-confirmed recent dengue. The number of female Aedes aegypti per person was the only significant (P = 0.02) household risk factor. The results of our study underscore the importance of intradomiciliary mosquito populations in dengue transmission, and may serve as a guide for mosquito control efforts.