Introduction
Although a few epidemiological and artificial infection studies in the 1970s indicated that dogs can be infected with influenza A virus (IAV), the IAV strain was not isolated from dogs until 2004(Payungpornet al. , 2008;Song et al. , 2008). This virus, now known as canine influenza virus (CIV), is responsible for canine influenza (CI), a respiratory disease in canines with the clinical features of cough, sneeze, fever, and nasal discharge. CIV was classified as the H3N8 and H3N2 subtypes, which were derived from interspecies transmission of equine and avian influenza virus, respectively(Sunet al. , 2017;Crawford et al. , 2005). H3N8 CIV was first documented in the USA in 2004 and later determined in the UK and Australia. H3N2 CIV was first reported in Korea in 2007. Subsequently, we also reported H3N2 CIV in China, indicating that this virus was circulating in Chinese canine population in 2006(Payungporn et al. , 2008;Lee et al. , 2010). In 2015, H3N2 CIV emerged in the USA, causing a large outbreak. Sequencing results and further analysis indicated that the virus might have been introduced from Korea(Voorheeset al. , 2018;Payungporn et al. , 2008).
In China, H3N2 CIV was detected in different canine populations, including pet dogs, farmed dogs, stray dogs, and even Tibetan mastiffs, which have a broad geographical distribution from southern to northern China(Chen et al. , 2018;Li et al. , 2018). The RNA polymerase of IAV lacks proofreading ability, and IAV continually mutates and evolves, which was also observed in CIV. However, since 2014, no studies on the isolation and genetic sequencing of H3N2 CIV in China have been published, and no related genetic information is available. In this study, we isolated emerging H3N2 CIV strains from sick dogs in China in 2018 and provide their genetic information.