There are two main types of simulation model for infectious diseases on networks: discrete-time and continuoustime models; of these, discrete-time simulations are more common, so we discuss them first. In a discrete-time simulation, at every time step, disease may be transmitted along every edge from an infectious node to a susceptible node with a particular probability (which may be the same for all extant edges or may vary according to properties of the two nodes or the edge). Also, nodes may recover (becoming immune, or reverting to being susceptible) during each timestep. Within a time-step, every infection and recovery event is assumed to occur simultaneously. In a dynamic network simulation, the network is typically updated every time step-for example, in a livestock movement network, during time-step x, infection could only transmit down edges that occurred during time-step x. Clearly, in a directed network, infection may only transmit in the direction of an edge.