Epidemiology and Molecular Characterization of Human Metapneumovirus in Influenza-Like Illness: A Decade of Surveillance in Dibrugarh, Assam (2014-2025).

BACKGROUND: Human metapneumovirus (hMPV) is a globally recognized cause of influenza-like illness (ILI), especially among children, but data from Northeast India are limited. This study analyzed epidemiological and molecular features of hMPV detected in Dibrugarh, Assam, over a decade-long surveillance period. METHODS: Between May 2014 and November 2025, 3,597 ILI patients were screened for hMPV at a tertiary hospital in Dibrugarh, Assam. Clinical samples (nasopharyngeal/throat swabs) were tested using multiplex respiratory panels and TaqMan-based real-time RT-PCR. Partial sequencing of the G gene was performed by Sanger sequencing, followed by phylogenetic and glycosylation analyses using MEGA 11, NetNGlyc, and NetOGlyc tools. Statistical analysis was done using SPSS v26. RESULTS: Overall, hMPV prevalence was 3.1% (112/3597), significantly higher among children aged <5 years than older individuals (3.9% vs. 1.3%; p = 0.003). hMPV activity exhibited marked winter seasonality, with significantly higher positivity during the colder months (5.6% vs. 0.8%; p < 0.001). Phylogenetic analysis demonstrated the circulation of A2.2.1 (A2b1), A2.2.2 (A2b2), and B2 lineages in Assam. The two 2025 A2.2.2 strains harbored the characteristic 111-nucleotide G-gene duplication, while comparative glycosylation analysis revealed lineage-specific variation in predicted N- and O-linked glycosylation profiles. CONCLUSION: hMPV remains an important cause of pediatric influenza-like illness in Northeast India, with marked winter seasonality. The detection of A2.2.1, A2.2.2, and B2 lineages, including A2.2.2 strains with the characteristic 111-nucleotide G-gene duplication, underscores the importance of continued molecular surveillance.