An Epidemic of Respiratory and Ocular Infections Caused by the Reemergence of a Recombinant Human Adenovirus, the Novel Type HAdV‐B114 (P7H3F3)

Human adenoviruses of species B (HAdV-B) can cause upper respiratory tract infections and conjunctivitis, but also severe lower respiratory tract infections (LRTI). Although HAdV-associated LRTI are non-notifiable in Germany, typing data of our Adenovirus Reference Laboratory indicated an HAdV-B3 epidemic in 2023, with 67 samples initially typed as HAdV-B3 compared to < 10/year in the previous years. Circulation of a novel, highly virulent HAdV-B3 strain was suspected and complete viral genomic sequencing performed, revealing a recombinant phylogeny of the penton gene (P), which originated from HAdV-B7, whereas hexon (H) and fiber (F) genes originated from HAdV-B3. Therefore, this virus was acknowledged by the Adenovirus Working Group as the novel recombinant genotype 114 (P7H3F3). Interestingly, BLAST search of the HAdV-B114 prototype sequence showed 99.91% identity to the old HAdV-B genome type 3a. Additionally, multiple complete adenovirus genomic sequences labeled as HAdV-B3 during the last two decades had > 99.8% identity, suggesting long-term circulation of HAdV-B114 although the recombinant phylogeny of its penton region had not been recognized. This detailed analysis of an HAdV epidemic associated with ocular and respiratory infections, including severe LRTI, led to the discovery of a novel genotype HAdV-B114, which is rather a neglected, re-emergent than an emerging virus.