The burden of dengue and risk factors of transmission in nine districts in Sri Lanka

BackgroundIt is crucial to understand the differences in dengue seroprevalence rates in different regions in Sri Lanka to understand the burden of infection to plan dengue vaccination programmes. Methodsage stratified seroprevalence rates were assessed in 5208 children, aged 10 to 19 years, in nine districts representing the nine provinces in Sri Lanka. A stratified multi-stage cluster was used to select 146 schools representing each district. Probability proportionate to the size (PPS) sampling technique based on the age distribution of general population and the urbanicity in each district was used to select the number of clusters to be enrolled for the study from each district. FindingsThe overall dengue seroprevalence rates in children was 24.8%, with the highest rates reported from Trincomalee (54.3%) and the lowest rates from Badulla (14.2%), which is a high altitude estate area. There was a weak but positive correlation between the dengue antibody positivity rates and age in districts which had seroprevalence rates of >25%, while there was no increase in antibody titres with age in the other districts. While the seroprevalence rates was significantly higher in urban areas (35.8%) compared to rural (23.2%) and estate areas (9.4%), there was no association with seropositivity rates with population density (Spearmans r=-0.01, p=0.98), in each district. InterpretationThe seroprevalence rates in many districts were <25% and the rates were very different to those reported from Colombo. Therefore, it would be important to take into account these differences when rolling out dengue vaccines in Sri Lanka. FundingWe are grateful to the World Health Organization and the UK Medical Research Council for support.