Frank, S. A. 1992. A kin selection model for the evolution of virulence. Proceedings of the Royal Society of London B 25:195-197.

The costs and benefits of parasite virulence are analyzed in an Evolutionarily Stable Strategy (ESS) model. Increased host mortality caused by disease (virulence) reduces a parasite's fitness by damaging its food supply. The fitness costs of high virulence may be offset by the benefits of increased transmission or ability to withstand the host's defenses. It has been suggested that multiple infections lead to higher virulence because of competition among parasite strains within a host. A quantitative prediction is given for the ESS virulence rate as a function of the coefficient of relatedness among coinfecting strains. The prediction depends on the quantitative relationship between the costs of virulence and the benefits of transmission or avoidance of host defenses. The particular mechanisms by which parasites can increase their transmission or avoid host defenses also play a key role in the evolution of virulence when their are multiple infections.