Department of Earth System Science Tsinghua University Beijing 100084 ChinaCenter for Healthy Cities Institute for China Sustainable Urbanization Tsinghua University Beijing 100084 China;
State Key Laboratory of Resources and Environment Information System Institute of Geographical Science and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China;
Influenza B viruses; Effective population size; Phylogeographic; Spatial dispersion; Mainland China;