Assessing the role of live poultry trade in community-structured transmission of avian influenza in China

Yang, Qiqi; Zhao, Xiang; Lemey, Philippe; Suchard, Marc A.; Bi, Yuhai; Shi, Weifeng; Liu, Di; Qi, Wenbao; Zhang, Guogang; Stenseth, Nils Chr.; Pybus, Oliver G.; Tian, Huaiyu

Community Structure Detection. Identifying community structures (38) is a crucial step in investigating networks that might explain patterns of viral spatial dissemination. In this context, a community is a group of nodes in a network such that intragroup connections are stronger or more numerous than intergroup connections (39, 40) ; the degree to which a network is subdivided into communities is measured as modularity (40) . Using the Walktrap community-finding algorithm (41) , with random walk length t = 5, we identified the community structure of 1) the live poultry trade networks and 2) the poultry egg trade network. Several community detection methods were compared (SI Appendix, Figs. S14 and S15), and the results indicated that current methods were appropriate for our study.