We model infectious disease dynamics using a simple stochastic susceptible-infectious-removed (SIR) epidemic model, with oneday time steps. Each individual moves independently through the three states: Susceptible (at risk of contracting the disease), Infectious (capable of transmitting the disease), or Removed (recovered or dead). Susceptible individuals can be infected by infected individuals from either its own group or other groups. The latter can occur during neighbour-neighbour contacts or travelerresident contacts.