Epidemiology of dengue infection in Ribeirão Preto, SP, Brazil

Abstract

OBJECTIVE: To assess dengue transmission in a correctional facility for juvenile delinquents in Ribeirão Preto, state of São Paulo, Brazil. METHODS: A serological and virology investigation was carried out among inmates and employees of a correctional facility for juvenile delinquents in Ribeirão Preto, Brazil. The study population consisted of 105 inmates and 91 employees representing 89% of the exposed. The collected blood was stored and processed using MAC-ELISA and virus isolation. A questionnaire was applied to each subject at the time of blood collection. RESULTS: Of the total of blood samples collected (n=196), 42 (21.4%) were positive for IgM antibodies and 43 (21.9%) for IgG antibodies; of which, 15 were both IgM and IgG positive and 28 (14.3%) were IgG positive only. Serotype 1 dengue virus was isolated in 5 samples. Out of 42 IgM positive samples, 14 (33.0%) subjects did not have any physical complaints. The incidence rate was 23.8% and 18.6% among inmates and employees, respectively. The first cases in the facility were reported in 1997 and the last ones in March 1997 though results are suggestive of an earlier onset of transmission. CONCLUSIONS: The high incidence rate of dengue infection can be explained by the high population density of the facility, high Aedes aegypti infestation, high numbers of asymptomatic subjects, and a higher transmission of disease in a closed setting.