ABSTRACT: Orthopneumoviruses have been found in humans and various animal hosts, including mice, cattle, dogs, and swine, in several countries, but have rarely been found in cats, with the only report being from the United States in 2010. This study is the first to detect feline orthopneumovirus (FPnV) in domestic cats in South Korea and the first to characterize the complete genomic sequence of the virus worldwide. FPnV was detected in 7 of 318 feline respiratory clinical samples, resulting in a detection rate of 2.2%. A complete genome sequence and a G gene sequence were successfully obtained from two FPnV-positive samples. Sequence analysis of these Korean FPnV strains (KFPnV-2201 and KFPnV-2202) showed the highest homology with the Korean swine orthopneumovirus (SOV) strain, KSOV-2201, which was recently identified in domestic pigs in South Korea. Surprisingly, KFPnVs showed relatively low homology with the FPnVs previously reported in the United States. As a result of phylogenetic analysis, FPnV strains previously reported in the United States were classified as genogroup 1, while two FPnV strains in Korea were classified as genogroup 2, along with four strains from the United States and Korea, and two canine orthopneumovirus (CPnV) strains in China. These results suggest that genetically diverse FPnV strains may be widely distributed globally, highlighting the need for continuous surveillance of the virus. Additionally, the high genetic homology among the viruses derived from different hosts, including cats, dogs, and pigs, suggests the possibility of cross-species transmission. These findings provide evidence that genetically diverse orthopneumoviruses are circulating in various animal hosts and that these viruses may be evolving through cross-species transmission. Therefore, further extensive studies are needed to understand the epidemiology, pathogenesis, and genetic evolution of FPnV.
