Molecular epidemiology and genetic characteristics of influenza viruses in a local pediatric population of eastern China, 2024

Introduction: The persistent circulation of influenza viruses following the COVID-19 pandemic remains a major public health concern, yet local genomic epidemiology in pediatric populations is not well-defined. Methods: In 2024, we collected 490 influenza antigen-positive specimens from a pediatric hospital in Qidong, eastern China, and performed influenza genome enrichment-based whole-genome sequencing, yielding 425 genomes (86.73%) with at least hemagglutinin (HA) and neuraminidase (NA) segments. Results: A/H1N1 (45.41%), A/H3N2 (18.35%), and B/Victoria (36.24%) co-circulated, with two activity peaks in January and December. Phylogenetic analysis assigned these viruses to clades 6B.1A.5a.2a (A/H1N1), 3C.2a1b.2a.2a.3a.1 (A/H3N2), and V1A.3a.2 (B/Victoria). Positively selected sites in HA included lineage-specific residues such as position 210 in B/Victoria and positions 187 and 372 in A/H3N2. The oseltamivir resistance marker NA-H275Y was detected in 7/193 (3.65%) A/H1N1 strains, whereas no detected resistance to RNA polymerase inhibitors. Discussion: These findings highlight the co-circulation patterns, genetic diversity, and antiviral susceptibility profile of influenza viruses in a pediatric population in eastern China, supporting the importance of sustained genomic surveillance to guide local prevention strategies and clinical management.