Fig. 7: The SIRS model.

There are three states: Susceptible (S), Infected (I), and Recovered (R). Accordingly, there are three parameters in the model: the transmission rate β determines the probability of transmission from an infected individual to a susceptible one; the recovery rate μ depicts the frequency with which an infected individual recovers and returns to the susceptible state; the re-susceptible rate γ determines the probability of individuals returning to the susceptible state after entering the recovered state.