Process. Infection transmission occurs during contact events between susceptible and infectious cases, which take place in the mixing groups. At the beginning of every Δt period (e.g., one hour), for each mixing group g, the simulation tracks the total number of infectious cases, n g , present in the group. It is assumed that each infectious case generates r g per Δt unit of time new contacts [46] , chosen randomly (uniformly) from the pool of susceptibles present in the group. We also assume the following: (i) during Δt period, a susceptible may come into contact with at most one infectious case and (ii) each contact exposure lasts Δt units of time. Once a susceptible has started her contact exposure at time t, she will develop infection at time t + Δt with a certain probability that is calculated as shown below.