The effects of the contact–density functions were investigated through a number of meaningful epidemiological parameters: (i) SIR dynamics, including prevalence (I/N); (ii) invasion probability, defined as the proportion of stochastic simulations in which the infection manages to survive the first year after introduction, conditional on having started successfully (successful start = infection persistence time > t0 + infectious period). This definition was chosen for simplicity, biological relevance and consistency with a previous model of MORV transmission ; and (iii) persistence probability, defined as the proportion of simulations in which the infection is still present at t = 10 years, conditional on having survived the first year.