Fig. 5.

Summary of epidemiological outcomes depending on the ESS of latency. If $\lambda *=0$, then the ESS is to have zero latency, and the model reduces to an SIRS epidemiological model (with a gamma-distributed infectious period). If $\infty >\lambda *>0$, then all hosts have milder symptoms in $I_1$ (individual-level interpretation), or a fraction of hosts in $I_1$ are fully asymptomatic (population-level interpretation). Finally, if $\lambda *\to \infty$, then the first stage of the infection can be considered fully asymptomatic. A single unstable interior evolutionarily singular strategy can also exist, giving rise to bistability with $\lambda *=0$ and $\lambda *\to \infty$ (green arrow).