The other dynamical rates, t and r are fixed indirectly. For the tracing rate, r, we vary the proportion of contacts successfully traced, e~r rzg T , between 0 and 1, which then determines r. For the infection transmission rate, t, we need methods for fitting to a given endemic equilibrium, in both stochastic and ODE contexts. Pairwise transmission fitting. In the case of fitting to an endemic state, we solve the algebraic equations generated by setting