  The stochastic SIRS model is a continuous-time Markov chain modelling the
spread of infectious diseases with temporary immunity, in a
homogeneously-mixing population of fixed size $N$. We study the scaling
behaviour of the extinction time of stochastic SIRS models as $N$ tends to
infinity. When the initial size of infected population is small, we obtain the
closed-form expression of the asymptotic distribution of this extinction time,
and compare it with the data from Monte Carlo simulation.
