Epidemiological and Molecular Characterization of Human Metapneumovirus (HMPV) in Children Under 14 Years of Age in Shijiazhuang City, China.

Objective: The objectives of this study were to analyze the epidemiological characteristics and whole-genome features of human metapneumovirus (HMPV) among children under 14 years of age in Shijiazhuang during 2022-2025, enrich the whole-genome data of HMPV in China, and provide a basis for further understanding the genetic diversity of the virus and for its prevention, control, and transmission intervention. Methods: A total of 1920 cases of acute respiratory infection were enrolled from three sentinel hospitals in Shijiazhuang. Nucleic acid screening was performed using real-time PCR. Whole-genome sequencing was conducted on 25 positive samples. Phylogenetic trees were constructed using the neighbor-joining method in MEGA, and nucleotide and amino acid sequence identity analyses were performed. Results: The overall detection rate of HMPV from 2022 to 2025 was 4.17%. A prominent peak in winter 2024 was the major distinguishing feature. Temporally, both influenza-like illness (ILI) and severe acute respiratory infection (SARI) cases showed marked seasonality during 2022-2025, with high-incidence periods in December-March and April-June. BLAST alignment and phylogenetic analysis showed that among the 25 sequenced HMPV specimens, genotype B2 was the most frequently identified genotype (13/25, 52%). Conclusions: HMPV epidemics in Shijiazhuang during 2022-2025 mainly occurred in winter-spring and spring-summer, with a notable detection peak in December 2024. The B2 genotype predominated among the sequenced HMPV isolates obtained in this study. The amino acid variation in the G gene was significantly higher than that in other genomic regions.