Genome-wide evolution and recombination of circulating human adenoviruses in Gwangju, South Korea, 2023-2025

Human adenoviruses (HAdVs) are important respiratory pathogens that circulate globally and frequently cause outbreaks, particularly among pediatric populations. Despite their clinical relevance, recent data on genome-wide evolution and recombination of circulating HAdVs in Korea remain limited. In this study, we characterized the epidemiological dynamics and genomic evolution of HAdVs detected in Gwangju, South Korea, between 2023 and 2025. Molecular epidemiological surveillance of respiratory samples was conducted, followed by phylogenetic and whole-genome sequencing analyses. Adenovirus positivity increased sharply during an outbreak from August to October 2023, with pediatric cases predominating. Phylogenetic analysis identified eight genotypes from species B and C, with genotype B114 as the principal outbreak strain. Whole-genome sequencing revealed recombination events in both species, involving antigenic, replication, and packaging regions. These findings indicate that circulating HAdVs undergo continuous genome-wide recombination, resulting in genotype-specific outbreaks that are not fully captured by capsid-based classification alone. Our study highlights the importance of whole-genome approaches for understanding adenovirus evolution and provides insights into the genomic diversity underlying recent outbreaks.