Dengue in South Asia: Emerging epidemiological patterns and surveillance obstacles

This systematic review synthesizes current knowledge on dengue epidemiology, serotype distribution, and surveillance systems across four South Asian countries: India, Bangladesh, Sri Lanka, and Bhutan. Through analysis of peer-reviewed literature (2000-2024) and official health reports, the study examines the historical progression from sporadic outbreaks to hyperendemic circulation of multiple dengue virus serotypes (DENV-1 through DENV-4). The findings reveal significant epidemiological shifts across the region, with all countries experiencing increasing case numbers, expanding geographic distribution, and evolving viral genetics. India demonstrates remarkable serotype diversity with all four serotypes circulating nationwide. Bangladesh has transitioned from epidemic to endemic transmission with sequential serotype dominance. Sri Lanka exhibits bimodal seasonal patterns with record outbreaks despite improved case fatality rates. Bhutan presents a unique case study of recent dengue establishment with concerning altitudinal expansion exceeding 1,800 meters. The review identifies critical surveillance challenges, including entomological indices with limited predictive value, significant under-reporting, diagnostic inconsistencies, and fragmented data management systems. Climate change and urbanization emerge as key drivers of transmission, extending vector ranges to previously non-endemic regions and creating abundant breeding habitats in rapidly developing urban centers. The study evaluates emerging approaches such as genomic surveillance, novel vector control technologies, digital reporting systems, and integrated surveillance frameworks. Recommendations include enhancing laboratory capacity, implementing climate-informed early warning systems, strengthening cross-border collaboration, expanding community engagement, evaluating novel control technologies, and establishing regional knowledge-sharing platforms. These findings provide evidence-based guidance for policymakers and public health practitioners to address the growing dengue burden in South Asia through improved surveillance and targeted interventions.