Dengue Virus Serotype Distribution and Disease Severity: Evidence from Molecular Surveillance in Karnataka, India

Dengue virus (DENV) infection remains a significant public health challenge in India, with increasing outbreaks and disease severity. The co-circulation of multiple DENV serotypes may influence clinical outcomes; however, data on serotype distribution and disease severity from many regions remain limited.

A hospital-based observational study was conducted in Belagavi, Karnataka, during 2024. A total of 351 serum samples from clinically suspected dengue patients were tested for NS1 antigen, immunoglobulin G and immunoglobulin M by Enzyme linked Immunosorbent Assay, followed by confirmation and serotyping by Real-Time PCR. Demographic, clinical, and laboratory data were analyzed to assess associations between DENV serotypes, disease severity, and complications.

Of 351 samples tested, 102 were NS1-positive, and 80 were confirmed by RT-PCR. All four DENV serotypes were detected, with DENV-2 predominating (38.7%). Mixed-serotype infections were observed, most commonly DENV-1 with DENV-2 and DENV-1 with DENV-3. Most of the patients were young adults aged 21-40 years (56.3%) with male predominance (67.5%). Thrombocytopenia was common, though severe thrombocytopenia occurred in only 10%. No significant association was found between serotype and disease severity in primary or secondary infections. Pleural effusion was the most frequent complication, mainly associated with DENV-2.

The study demonstrates the co-circulation of all four DENV serotypes in Belagavi during 2024, with DENV-2 predominance. Disease severity was not significantly associated with specific serotypes, highlighting the role of host and disease-related factors. Continuous molecular surveillance is essential to monitor evolving serotype dynamics and inform dengue control strategies.