We present a class of computational epidemic models that integrate transportation and census data on the worldwide scale. The defined models allow the analysis of the impact of complex mobility networks on the behavior of emergent disease spreading and the general issue of the predictive power offered by computational approaches. In this framework it is possible to tackle foundational issues by using the particle network approach and provide new mathematical and computational tools for the study of large scale epidemics. We will focus the discussion on the analysis of invasion thresholds and the definition of epidemic pathways. Based on these results we present the Global Epidemic Modeler (GEM) computational platform that can be used in the analysis of intervention and mitigation policies for emerging disease outbreak.