← Back to Gallery

Pathogen Virulence Evolution

Trade-Off Hypothesis: Transmission vs. Host Mortality

Host Population

10,000
0.010
0.10

Trade-Off Parameters

1.50
1.0 (linear)

Strain Competition

0.05
0.15

Trade-Off Hypothesis

Parasites face a trade-off: higher virulence (ν) increases transmission (β) but shortens infection duration.

R₀ = β(ν) / (μ + ν + γ)
β(ν) = β_max × (ν / (ν + k))

Optimal virulence maximizes R₀. With competition, virulence often increases.

Strain 1 (low ν)
Strain 2 (high ν)
Optimal Virulence
R₀ Curve
Strain 1 Prevalence
0%
Strain 2 Prevalence
0%
Optimal Virulence
0.00
Generation
0
Strain 1
Virulence: 0.05
β: 0.00
R₀: 0.00
Duration: 0 days
Strain 2
Virulence: 0.15
β: 0.00
R₀: 0.00
Duration: 0 days
Predicted Winner
Higher R₀: -
Competitive Outcome: -