As before, we have a wildtype pathogen capable of acquiring adaptations for human transmission. Assume a finite number of hosts in the village, and an effectively infinite number in the city. To allow for daily commuting, we label individuals in the city according to whether they are commuters from the village or not (neglecting commuters originating from the city and present in the village). The superscripts (v),(c) represent village and city inhabitants respectively, while (vm) denotes villagers in the city. Village members commute to the city at a per capita rate x 1 , and return at per capita rate x 2 . At any one time, a proportion w of villagers, the commuters, are in the city with w being set by x 1 and x 2 as described below. Further, we neglect susceptible village commuters acquiring infection in the city (this arises formally from the infinite number of hosts in the city). The number of village residents is fixed at N~N (v) zN (vm)~1 000, and we define the average number of commuters as Village, non-commuting : Village, commuting :