Degree heterogeneity lowers the epidemic threshold
S: -I: -R: -R₀: -λc: -
Heterogeneous mean-field (Pastor-Satorras & Vespignani 2001): for scale-free networks with P(k)~k^−γ and γ≤3,
the epidemic threshold λ_c = <k>/<k²> → 0 as N→∞. Hubs act as super-spreaders.
R₀ = (λ/μ)·(<k²>/<k>). Try both network types and compare outbreak sizes.