In Figure 4 , we extract the probability of emergence per introduction given a certain number already infected. These data are easily calculated using the outbreak size distribution and the probability of emergence per introduction. Assume an introduction has caused x infectious hosts already. The probability of extinction is the cumulative probability of getting an outbreak size equal to or larger than x, renormalized by all possible outcomes (extinctions and emergences) once x hosts are infectious. This yields the probability of emergence per number of infected. In Figure 4 , the effect of spatial heterogeneity can be seen directly. For vcw §10, the village-city simulations agree very well with the analytical results assuming a single, infinite population. But for vcw~1, the probability of emergence converges to approximately 0:42.