The model is used to generate epidemic trees [42, 43] . We sample 1000 parameter sets from the joint posterior distribution and calculate the probability of infection for each potential infector city. The most likely tree for each parameter set is generated by calculating which 'infector' city has the highest probability of infecting each 'infectee' city. The distance to this infector, the probability of the infector-infectee pair and the number of infectees each infector creates are calculated for each parameter set. Mean values are weighted by the frequency of infector -infectee pairs from 1000 trees.