Gillespie SSA Epidemic
Exact stochastic SIR · Next-reaction method · Ensemble trajectories
Pop Size (N)
200
β (infection)
0.40
γ (recovery)
0.15
Runs
8
Run SSA
Susceptible
Infected
Recovered
Gillespie:
τ ~ Exp(a₀), reaction k chosen ∝ aₖ
Rates:
a₁=βSI/N, a₂=γI
R₀ = β/γ
— threshold: R₀>1 → epidemic