Molecular characterization of dengue virus serotypes: Dominance of DENV-3 and evidence of co-infections in an Indian cohort

Abstract

Introduction: Dengue is a major mosquito-borne viral disease of global concern, characterized by diverse clinical presentations and frequent outbreaks in India. Accurate diagnosis and serotype surveillance are essential to guide clinical management and public health strategies. Aims and Objectives: This study aimed to determine the distribution of dengue virus serotypes and identify possible mixed infections in a regional cohort. Materials and Methods: A total of 244 patients with laboratory-confirmed dengue were enrolled. Serum samples were screened using NS1 antigen and IgM antibody ELISA, and molecular confirmation with serotyping was performed by multiplex real-time RT-PCR. Results: Of the 244 cases, 128 (53.5%) were positive for NS1 antigen, 80 (32.7%) for IgM antibodies, and 36 (14.8%) for both. Viral RNA was detected in 141 patients (57.8%) by RT-PCR. All four dengue virus serotypes were identified, with a clear predominance of DENV-3 (87.2%), followed by DENV-2 (6.4%), DENV-1 (5.7%), and DENV-4 (0.7%). Mixed infections were observed in five cases (2.0%), including DENV-1 with DENV-3 and DENV-3 with DENV-4. No significant association between serotype and clinical manifestations was observed; fever, myalgia, and headache were the most common presenting symptoms. Cases peaked during the monsoon and post-monsoon months, reflecting favorable vector breeding conditions. Conclusion: The study highlights the co-circulation of all four dengue virus serotypes, the predominance of DENV-3, and the presence of rare mixed infections, indicating progression toward hyperendemicity in the region. Continuous molecular surveillance is therefore critical to guide outbreak preparedness, strengthen clinical care, and support the planning of future vaccine strategies.