Dengue molecular dynamics: viral load and serotype shifts predict severity and death in Kolkata, Eastern India

Dengue manifestations range from mild fever to fatal shock, driven by viral virulence and host responses. While Kolkata is hyperendemic, data linking specific serotypes and viral load to clinical outcomes remains limited.

This prospective observational study (January 2024-June 2025) analysed 120 dengue serology-reactive patients at a Kolkata teaching hospital. Viral nucleic acid was extracted for serotyping and quantification via the molecular method. Patients were stratified by severity using World Health Organization 2009 criteria.

Dengue 2 serotype (DENV-2) was dominant (45.8%), followed by dengue 3 serotype (DENV-3) (33.3%) and coinfections (20.0%). Severe cases had significantly lower mean cycle threshold (Ct) values (23.4 vs 28.1; p<0.001). Multivariate analysis identified high viral load as an independent predictor of severity (adjusted odds ratio 0.89 per unit Ct decrease, p=0.003), indicating an 11% risk increase per unit Ct decrease. Notably, DENV-3 exhibited a strong trend toward higher mortality (adjusted odds ratio 3.31, p=0.08), accounting for 53.8% of fatal cases despite lower viraemia.

The study identifies a 'prevalence-virulence dissociation' where DENV-2 dominates numerically but DENV-3 drives mortality. Quantitative viral load is a robust prognostic marker. Integrating real-time molecular surveillance and Ct threshold into triage protocols is vital for mitigating fatal outcomes in hyperendemic regions.