Seroprevalence of dengue in urban and rural settings in Kerala, India

Dengue fever is a major public health concern in India and Kerala is one of the worst affected states in the country. Kanjirappally, Kottayam district, has been reported to be the epicentre of dengue in the state. In 2016, we carried out a post-epidemic seroprevalence survey in both urban and rural sites of this endemic foci to estimate the disease burden. A systematic sampling technique with a random start (household) was adopted in each study site. Overall, 938 individuals were enrolled in the survey, 470 in the urban and 468 in the rural sites belonging to 103 and 88 households respectively. Rapid diagnostic IgM/IgG test kit was used for the study. The overall dengue IgG seroprevalence observed was 51.28%. Urban sites had higher seroprevalence rate (59.8%) compared to rural sites (42.74%, P < 0.01). No gender difference was recorded in seroprevalence rates among the sites. Exposure was found to be more common among adults than children in both areas. Seroprevalence rate in children <10 years of age was found to be 15 times higher (44.61%) in urban sites, than that in the rural sites (3.03%). The present study indicates that more than half of the population is exposed to DENV (dengue virus) infection in this oldest focus of dengue in Kerala.