High Sero-Prevalence of Dengue IgG Antibodies among Healthy Individuals in Andhra Pradesh, India

Dengue fever (DF), dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS) are increasing in India and Andhra Pradesh. Most cases of DHF and DSS occur at the time of secondary dengue virus infection. It is critical to know, the proportion of population exposed to dengue virus infection; therefore at risk of developing DHF or DSS. We assessed the approximate extent of exposure to Dengue virus infection in Hyderabad, Andhra Pradesh.

A convenience sera sample from 200 apparently healthy individuals attending routine health checkup at a medium-sized urban reference laboratory was collected. The samples were assayed for antidengue IgG; in first phase using Dengue IgG Capture ELISA and IgG Indirect ELISA; and in Confirmatory phase using Plaque Reduction Neutralisation Test (PRNT).

Sero-positivity of 10.5% (21 of 200) with IgG Capture ELISA and 89.5% (179 of 200) with IgG Indirect ELISA was seen in first phase. 100% sero-positivity was seen in the samples of age ≥ 40 years by Indirect ELISA. In the confirmatory phase, 75% of Indirect ELISA positive samples tested positive with PRNT. Of the 12 randomized blinded samples, all Indirect ELISA negative samples were negative and 5 of the 6 Indirect ELISA positive samples were positive with PRNT. There was a positive correlation between the two assays.

The high sero-positivity dengue IgG of 89.5% indicates that the study population has been exposed to Dengue virus infection. This study warrants the need for further large scale population based studies and identification of circulating serotypes.