Surveillance of respiratory pathogens: emerging seasonal patterns from western India

Detection and monitoring of SARS-CoV-2, influenza A/B and RSV are critical for clinical management and public health planning, especially in tropical settings. We analysed data from a tertiary care hospital in Mumbai, Western India over three years using the Xpert Xpress CoV-2/Flu/RSV multiplex assay. Upper respiratory specimens were tested between July 2022 and June 2025 and de-identified data was retrospectively reviewed. Overall and annual pathogen prevalence (SARS-CoV-2, influenza A/B, RSV) rates were calculated, age and sex distributions, monthly seasonal trends, and co-infection patterns were reviewed. Ethics approval was obtained and patient consent waived. Among 2,860 specimens, 645 (22.55%) tested positive for influenza A, 96 (3.35%) for influenza B, 86 (3.0%) for RSV, and 199 (6.95%) for SARS-CoV-2; 1,852 (64.75%) were negative. Co-infections, though relatively uncommon, were observed in various combinations in a total of 18 cases over three years. Year-wise, influenza A remained most prevalent across the years, influenza B and RSV showed variable annual peaks with relatively higher frequencies in 2023-24, and SARS-CoV-2 showed a declining but persistent presence. Overall pathogen detection was higher in the paediatric group than in adults, with RSV positivity significantly greater in children (10.3% vs. 2.1%, p < 0.00001). A distinct seasonal pattern was evident, with the highest positivity observed during the monsoon and early post-monsoon period (June to September) each year, marking the peak transmission period in this region. Influenza A remains the dominant pathogen among respiratory virus-positive patients in Mumbai, with notable seasonality synchronous with monsoon/post-monsoon periods. RSV circulates mainly among young children, while SARS-CoV-2 persists at lower rates. Multiplex molecular surveillance provides actionable epidemiologic insights in high-burden tropical urban settings.