As India prepares to roll out its first dengue vaccine as early as next year, the country's first nationwide mapping of dengue virus strains has found that all four serotypes are circulating simultaneously in eight states and Union Territories, a finding that researchers say could shape vaccination strategy since infections involving multiple strains are linked to more severe disease, according to Anuja Jaiswal's Times of India report.
The pan-India molecular surveillance study, conducted by the ICMR-National Institute of Virology (NIV), Pune, analysed 6,889 laboratory-confirmed dengue samples collected through 45 Virus Research and Diagnostic Laboratories (VRDLs) across 25 states and Union Territories between 2023 and 2025. The analysis found that at least two dengue serotypes were co-circulating in every state and UT covered under the surveillance, pointing to increasing hyperendemicity of dengue in India.
According to the study, all four dengue serotypes—DENV-1, DENV-2, DENV-3 and DENV-4—were detected simultaneously in Andhra Pradesh, Gujarat, Haryana, Madhya Pradesh, Maharashtra, Rajasthan, Tamil Nadu and West Bengal. Another 15 states and UTs reported the circulation of three serotypes, while the remaining two recorded two serotypes.
The findings showed that DENV-2 remained the dominant strain, accounting for 51% of infections, followed by DENV-3 (13%), DENV-1 (7%) and DENV-4 (1%). Around 7% of patients were simultaneously infected with two or more dengue serotypes.
Researchers found that patients with concurrent infections were more likely to develop thrombocytopenia, haemorrhagic manifestations and arthralgia than those infected with a single serotype, indicating that the circulation of multiple strains could increase the burden of severe dengue.
The researchers said continuous molecular surveillance would be critical to track changes in dengue virus circulation, strengthen outbreak forecasting and support vaccine deployment strategies. They noted that several dengue vaccine candidates are in advanced stages of development and that vaccine effectiveness differs across serotypes, making surveillance data crucial for immunisation planning.
The study also highlighted significant regional variation in serotype distribution. While DENV-2 was the predominant strain nationally, DENV-1 accounted for a higher share of infections in Tamil Nadu (29%), Haryana (38%) and Rajasthan (25%). DENV-3 was more prevalent in Gujarat (30%), Tamil Nadu (29%), Uttar Pradesh (29%) and West Bengal (20%).
(With TOI inputs)
