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].