Incidence and healthcare costs of symptomatic dengue in an urban, city-wide cohort in South India

BACKGROUND: Gaps in India’s routine dengue surveillance have led to an underestimation of its actual burden and could adversely affect funding for preventive public health measures. In this study, we report the incidence of symptomatic dengue and the associated direct medical costs in a large urban population-based cohort in Vellore, Tamil Nadu. METHODS: Surveillance for febrile illnesses was conducted in 30 urban wards in Vellore as part of the Vellore Typhoid Vaccine Impact Trial. Participants seeking healthcare for febrile illnesses called the trial helpline, triggering active surveillance until fever defervescence. Febrile episodes lasting ≥ 3 days were diagnosed as dengue based on either laboratory tests or a physician-assigned diagnosis. RESULTS: From May 2023 to January 2025, 74,587 participants aged 1–30 years contributed 124,018.4 person-years (PYs) of follow-up. We identified 188 laboratory-confirmed and 107 physician-assigned diagnoses of dengue. From May 2023 to April 2024, the incidence of laboratory-confirmed dengue was 150.3 per 100,000 PYs (95% confidence interval [CI]: 124.4–181.7), and 205.2 per 100,000 PYs (95% CI: 174.4–241.3) for all dengue cases. The median direct medical cost for laboratory-confirmed dengue treated as outpatients was Indian Rupees (INR) 4,357 (interquartile range [IQR]: 2,432–7,204), and INR 16,827 (IQR: 9,556–26,348) for those who were hospitalised. CONCLUSIONS: The incidence of dengue and its associated treatment costs were high in this urban setting. Strengthening routine disease surveillance with enhanced diagnostic testing and systematically collected data from the private sector will provide better estimates of the dengue burden in India and inform policy decisions.