The village's number of residents in our commuting model is sufficient to avoid finite size effects on the outbreak size. Furthermore, it is independent of any spatial heterogeneity. The number of residents only has a limiting effect on the outbreak size distribution. Figure 3B shows the outbreak size distribution for our short-term commuting model. The average number of commuters ranges from 1 to 100. As we expect, no significant effect on the outbreak size distribution can be seen, even for vcw~1. It validates our assumption of the independence of infectious hosts, necessary for a branching-process formulation, as the simulations closely match the analytical predictions. It is noteworthy here that only the biology of the novel pathogen determines the emergence process, as outbreak sizes group according to the intermediate average reproductive number a 2 . The minimal deviation for vcw~100 commuters is based on the fact that the effective village size is only N (v)~9 00 due to the absent commuters.