Human Adenovirus B114 (P7H3F3): A Neglected Re-Emergent Pathogen Long Misclassified as HAdV-B3 With Novel Genomic Variations.

Acute respiratory infection (ARI) outbreaks in Beijing caused by human adenovirus B114 (HAdV-B114) have long been misclassified as HAdV-B3. Its origin, evolutionary trajectory and long-term transmission dynamics remain poorly understood. This study aimed to clarify its epidemiological characteristics, genomic variations, recombination features and evolutionary history. Among 51 HAdV outbreaks in Beijing from 2017 to 2024, 32 originally designated as HAdV-B3 were studied. Viral isolation was performed on 267 positive samples, conducted targeted and whole-genome sequencing, and carried out phylogenetic, amino acid variation, recombination and Bayesian analyses on core capsid genes. All 32 outbreaks were confirmed to be caused by HAdV-B114, which had circulated in Beijing since 2017, mainly causing outbreaks among young primary school students. We obtained 177 isolates, and successfully acquired penton, hexon and fiber genes from 127 strains. These three genes were fully identical in isolates from the same outbreak, so one strain per outbreak was selected as representative. Phylogenetic analysis showed its penton gene clustered with HAdV-B7, while hexon and fiber genes resembled HAdV-B3. Compared with HAdV-B114 reference sequence, variants had mutations and insertions in hexon and penton. 34-nt deletion mutants of HAdV-B114 were discovered in the 2023-2024 outbreaks, and they were confirmed as HAdV-B3/B7 recombinants. The most recent common ancestor (tMRCA) of HAdV-B114 penton gene divergence was 1993.718, and variant 24SYYQ0247 formed an independent sublineage. HAdV-B114 is a misidentified re-emergent virus that has long circulated in Beijing and achieved widespread prevalence. Sustained adenovirus molecular surveillance is essential for ARI prevention.