Fig. 1.

The dashed curve is the ODE solution of $I\left(t\right)$ in the SIR model and the other curves are four sample paths of the SIR CTMC model. Parameter values are $\beta =0.3$, $\gamma =0.15$, and either $N=100$ (top graphs) or $N=750$ (bottom graphs). The initial conditions are $S\left(0\right)=98$ and $I\left(0\right)=2$. The graphs on the right are a close-up view on the time interval $\left[\mathrm{0,15}\right]$ of the graphs on the left. The value $\mathrm{\mathbb{P}}=0.25$ is the estimate for the probability of a minor outbreak. On average, one sample path out of four hits zero, given ${\mathcal{R}}_0=2$ and $I\left(0\right)=2$.