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

Poultry Transportation Network Reconstruction. Province-level networks of poultry transportation (Fig. 3 and SI Appendix, Fig. S6 ) were constructed from statistics of poultry egg production and populations of domestic poultry, using a classic gravity model. This model is supported by crosssectional surveys of poultry transportation in Cambodia (36) and Vietnam (37) . In summary, the flux of live poultry or poultry egg transport (G ij ) between provinces i and j separated by geographic distance d ij takes the form G ij = N i N j d ij −1 , where N i is the number of live poultry (unit: 10,000 poultry) or the amount of poultry egg production (unit: ton) in source province i (averaged across years) and N j is human population size (unit: 10,000 people) in destination province j (averaged across years). Other gravity-model parameterizations were tested, and the results showed that the network structure we determined is robust to the parameterization.