Dual IgM seropositivity for dengue and chikungunya among suspected dengue cases: A hospital-based observational study from Northwestern Karnataka

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Purpose Dengue virus (DENV) and Chikungunya virus (CHIKV) are significant arboviruses transmitted by Aedes mosquitoes. The concurrent circulation of these viruses complicates syndromic diagnosis and subsequently, the clinical management in endemic settings like India. Objective The present study evaluated the prevalence and clinical features of dengue immunoglobulin M (IgM) and dual IgM seropositive patients (dengue and chikungunya) among a subset of patients presenting with clinical suspicion of dengue fever admitted in tertiary care settings in Belagavi, Northwestern Karnataka, India. Methods A retrospective observational study was conducted using serum samples received from tertiary care hospitals in Belagavi, Karnataka between January 2024 to October 2025. Of 151 clinically suspected dengue cases, 94 patients with complete clinical records and available serum samples were included. Dengue virus (DENV) and chikungunya virus (CHIKV) IgM antibodies were detected using Indian Council of Medical Research - National Institute of Virology (ICMR-NIV) Immunoglobulin M Antibody Capture (MAC) Enzyme Linked Immunosorbent Assay (ELISA) kits. The reported sensitivity and specificity were 98.53% and 98.84% for DENV IgM ELISA and 95% and 98% for CHIKV IgM ELISA, respectively. Results Dual IgM seropositivity to dengue and chikungunya was observed in 19 patients (20.2%); whereas 73 (77.7%) were positive only for dengue IgM and 2 (2.1%) were negative for both assays. No isolated CHIKV IgM positivity was detected. Dual-positive patients exhibited predominantly dengue-like illness, characterized by myalgia (57.9%), thrombocytopenia (median platelet count, 70,000 cells/mm 3 ) and elevated aspartate transaminase (AST) levels (median AST, 67 U/L). Conclusions Dual IgM seropositivity for dengue and chikungunya was observed in 20.2% of suspected dengue cases. While IgM serology cannot confirm concurrent infection, these findings suggest co-circulation of both arboviruses and highlight the need for integrated arboviral surveillance in endemic regions.

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