3.1 The distribution of the samples detected in 2019
A total of 3160 swab samples were collected in 14 provinces of China in 2019 (Anhui, Guangdong, Guangxi, Hebei, Hubei, Jiangsu, Jiangxi, Jilin, Ningxia, Qinghai, Shanghai, Sichuan, Xizang, and Yunnan), and the geographical distribution of the samples detected in this study were shown in Figure 1 . All samples including 2238 chicken samples, 669 duck samples, 184 pigeon samples, 59 geese samples, 15 other avian samples (10 from wild geese, 5 from partridges)and originated from 48 retail markets, 18 wholesale markets, 4 slaughterhouse, 18 poultry farms.