Genomic Recombination and Genetic Diversity of Emerging Novel Duck Orthoreovirus in China, 2018–2023

Novel duck orthoreovirus (NDRV) represents a major pathogen severely affecting the waterfowl farming industry in China, yet its evolutionary dynamics and reassortment patterns remain poorly defined. In this study, we sequenced the full genomes of 10 NDRV isolates obtained from Shandong and Jiangsu provinces (2018–2023) and analyzed their genetic features through sequence identity, phylogenetics, and reassortment detection. We also evaluated pathogenicity in 1‐day‐old ducklings for three representative isolates via intravenous injection. Our results show that nucleotide (nt) homologies across all gene segments ranged from 86.9% to 99.9%, and the L2, M1, S2, and S4 segments displayed greater sequence variability than the traditionally hypervariable S1 gene in our isolates. We identified recombination events in the M2 segment of strain XT18 (with SDYC and HN5d as parental strains) and the S4 segment of strain LY20 (with GX‐Y7 and SDYC as parents), which, to our knowledge, represent the first reports of recombination in the M2 and S4 segments of NDRV. In pathogenicity tests, strain SDYC induced the most severe splenic lesions and maintained the highest viral loads in vivo. Collectively, these findings clarify the molecular evolution and reassortment landscape of currently circulating NDRV strains and offer a scientific basis for selecting vaccine candidates and designing precision control strategies.