Sample Collection
We collected samples of Oropharyngeal and cloacal swabs from live poultry markets in the Guangdong Province, including Guangzhou, Shenzhen, Foshan, and Zhanjiang cities. A small number of samples of clinically suspected avian influenza were collected from other Provinces (including Jiangsu, Guangdong, Shandong, Henan, Hebei, Guangxi, and Henan) during 2017-2019, China. All of the samples were inoculated into 9-day-old embryonated chicken eggs for virus isolation individually. The HA subtype of the viruses was confirmed using the hemagglutinin inhibition (HI) test. H5N6 strains were isolated from live poultry markets. In addition, H9N2(Jin et al., 2020), H7N9(Qi et al., 2018), H6N6, H6N2, H3N2, H3N8(Li et al., 2019), H1N1, and other subtypes were also isolated. In this study, ten strains of the H5 subtype avian influenza were selected to sequence the full gene sequence, and four strains were selected to determine the virulence by developing animal experiments[EPI_ISL_402100, EPI_ISL_422383-EPI_ISL_422396].