The SIR Model

Susceptible, infected, recovered

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• SIR: $S \to I \to R$, with $R_0 = \beta/\gamma$.
• Infections peak when $S = 1/R_0$.
• Outbreaks overshoot the herd immunity threshold.

Steps

1. Three groups
2. An outbreak unfolds
3. When does it peak?
4. Keep the peak down
5. How high the peak
6. The final size