Burden of Measles and Rubella Virus among Paediatric Patients Presenting with Febrile Maculopapular Rash at a Tertiary Care Centre in Ballari, Karnataka, India

Background: Sustained measles–rubella elimination requires sensitive and specific laboratory confirmation of clinically suspected cases. In surveillance settings, IgM capture enzyme-linked immunosorbent assay (ELISA) remains the primary diagnostic method. As disease incidence declines, assay reliability and quality assurance become increasingly critical. Objectives: To determine the proportion of laboratory-confirmed measles and rubella infections among paediatric patients presenting with febrile maculopapular rash along with assessment of MR vaccination within a tertiary care surveillance laboratory. Study Design: A retrospective laboratory-based study was conducted from August 2024 to July 2025 at the Virus Research and Diagnostic Laboratory, Department of Microbiology, Ballari Medical College and Research Centre, Ballari, Karnataka, India. Serum samples from paediatric patients (≤15 years) meeting the clinical case definition for measles or rubella were tested for virus-specific IgM antibodies using capture ELISA. Results: Fifty-seven laboratory-confirmed cases were identified. Measles IgM was detected in 56 (98.2%) cases, rubella IgM in 4 (7.0%), and dual IgM positivity in 3 (5.3%). The highest incidence occurred in children aged 6–10 years (36.8%). Incomplete vaccination was significantly associated with measles infection (OR 2.8; 95% CI 1.1–7.3; p = 0.041). Conclusions: Measles remains the predominant cause of febrile rash illness in this region. IgM capture ELISA demonstrated consistent analytical performance and remains an appropriate confirmatory tool for routine surveillance. Addressing vaccination gaps is essential for regional elimination efforts. Key words: Measles, Rubella, IgM ELISA, Virus Research and Diagnostic Laboratory, Ballari