Thanks to
https://insightmaker.com/insight/25229/SIR-model-with-stochastic-events
for this example of adding stochasticity to the SIR model. "A simple extension of the tutorial SIR example, adding in Poisson events for infection and recovery. There is one macro, RandPoissonStep(rate)... to simulate Poisson processes."

I've tried to add in the infection step, as well as turn numbers into integers (without much luck). But it certainly has some interesting dynamics! I've also added in a phase plane graphic.