Fitness contours for rare disease variants in the absence of non-replicators.

<p>(A) Pathogen longevity (1/<i>d_V</i>) – Mutation probability (<i>x</i>) and (B) Yield strength (<i>ε</i>) – Mutation probability (<i>x</i>). Long-lived pathogens and/or high yielding pathogens favoured the invasion of novel disease variants (those that have higher fitness). [Shading: black (low fitness) to white (high fitness)]. (Fitness is the dominant eigenvalue from equation 12).