Incidence of primary dengue virus infections in Southern Vietnamese children and reactivity against other flaviviruses

Objective: To study the incidence of asymptomatic primary dengue infections among children and reactivity against other flaviviruses. Methods: A total of 216 children, who had no dengue-specific IgG antibodies during a serosurvey in 2003 were re-examined 23 months later to determine if seroconversion had occurred. Dengue-specific IgG was demonstrated with enzyme-linked immunosorbent assay (ELISA) and reactivity patterns against other flaviviruses were assessed by using immunofluorescence assay (IFA). Results: Sixty-six children had seroconverted for dengue virus-specific IgG; the true annual incidence of primary dengue was thus 17.3% (95% CI: 13.8-21.4). Japanese Encephalitis virus (JEV)-specific IgG antibodies were detected by IFA among three (4.6%) samples that showed seroconversion in the dengue ELISA, because of cross-reactivity. Conclusion: Our findings highlight the high incidence of dengue among Vietnamese children; JEV infections are rare. The true annual incidence of dengue can be estimated with a single cross-sectional seroprevalence survey.

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