Tracking the clinico-microbiological profile and molecular characterization of dengue cases during the monsoon-season in Belagavi, Karnataka

This study aimed to identify and characterise circulating DENV serotypes during the 2024 monsoon season in Belagavi, Karnataka and to analyze the clinical and demographic profiles of the hospitalized dengue cohort and correlate these patterns with the identified serotypes. A prospective, hospital-based observational study was conducted at a tertiary care centre in Belagavi, Karnataka, from June to September 2024. A total of 89 dengue-confirmed cases out of the 794 dengue-positive cases detected using NS1 antigen and IgM antibody by ELISA technique were subjected to serotyping by RT-PCR targeting the CprM gene. A subset of positive RT-PCR specimens was subjected to sequencing and phylogenetic analysis. The clinical details were analysed for demographic features, clinical manifestations, and diagnostic test results to establish correlations with serotype distribution. Of the 89 positive dengue patients, 28 (31.46%) were confirmed positive for dengue virus NS1 antigen by ELISA, while 87 (97.75%) patients tested positive for anti-dengue IgM antibodies. Dengue serotyping of the 28 NS1-positive samples was carried out, of which 23 (82.1%) were positive. DENV-2 (91.3%) was the predominant serotype, followed by DENV-1 and DENV-3, each identified in one case (4.3%, respectively). Genetic analysis of DENV-2 isolates revealed close phylogenetic relationships with the strains from Bhopal, indicating possible regional transmission dynamics. Fever and myalgia were the predominant symptoms across all serotypes, while chills, headache, and retro-orbital pain were associated with DENV-2. The present study is the first comprehensive molecular surveillance report from the northern part of Karnataka demonstrating the predominance of DENV-2 serotype, with distinct clinical and demographic patterns. The high proportion of late-phase diagnoses of dengue underscores the need for improved early detection strategies and timely interventions to manage dengue outbreaks, especially during high-risk transmission periods. These results underline the importance of continuous molecular surveillance to track viral evolution and monitor serotype shift and genetic variations.