Fig. 1. The distribution of sampling sites and avian influenza viruses (AIVs) in LPMs across China.

a Map of the AIV sampling sites and isolation rates in LPMs. AIV surveillance sites in 37 cities (indicated by black dots) of 23 provinces or municipalities or minority autonomous regions in China are divided into seven different regions: North (Inner Mongolia, NM and Jilin, JL; orange), East-Central (Shanxi, SX; Ningxia, NX; Shandong, SD; Shaanxi, SaX and Henan, HeN; light green), South-Central (Anhui, AH; Hunan, HuN; Jiangxi, JX and Fujian, FJ; yellow), Yangtze River Delta (Jiangsu, JS and Zhejiang, ZJ; pink), South-West (Sichuan, SC; Chongqing, CQ; Yunnan, YN; and Guizhou, GZ; orange red), South (Guangxi, GX; Guangdong, GD and Hainan, HaN; dark green), and West (Xinjiang, XJ; Qinghai, QH; and Xizang, XZ; light purple). The red portion in each pie chart indicates the isolation rate of AIV in this region. The standard map was downloaded from Ministry of Natural Resources of the People’s Republic of China (http://bzdt.ch.mnr.gov.cn/), and the collection sites of LPMs in our study were marked on the map using ArcGIS. b AIV positive rates of the present study (2016–19) and the previous study in 2014–16¹³. The regions included North, East-Central, South-Central, Yangtze River Delta, South-West, and South. The numbers on the column represent the AIV isolation rate. c Subtype proportions of AIVs in the pure isolates with a single HxNy subtype. d The proportion of HA and NA from the impure isolates containing over two HA or NA subtypes. Source data are provided as a Source Data file.