Figure 1: The sequencing of 218 HPAI H5N1 viruses sampled from mainland China.

(a) Number of HA sequences for HPAI H5N1 virus sampled per province of mainland China. The number in the brackets refers to the number of newly sequenced viruses. Provinces in southern China are in bold text. (b) A map of China showing the all provinces, and, in grey, provinces in which epidemics caused by HPAI H5N1 virus were identified in the year 2013. The heavy gray line indicates the position of the Qin Mountains and Huai River that divide northern and southern China. The map was reconstructed using OpenStreetMap (http://www.openstreetmap.org/), licensed on terms of the Open Database License, “ODbL” 1.0 (http://opendatacommons.org/licenses/odbl/), and is for illustrative purposes only. (c) The number of provinces with epidemics caused by HPAI H5N1 virus inferred from HA sequences in mainland China from 1996 to 2015.