Epidemiology meets evolutionary ecology

The rapid expansion and increasing mobility of human populations make understanding the evolution of parasite virulence a public health priority. The potential for the swift evolution of virulence in response to changes in host ecology has motivated the integration of evolutionary ecology with epidemiological theory, as part of the emerging field of evolutionary epidemiology. Virulence is the product of complex interactions among evolutionary, ecological and epidemiological processes. Recent models that incorporate ideas from both evolutionary ecology and epidemiology generate predictions that could not be made by either discipline alone. These models predict that the ecological or evolutionary changes affecting population dynamics of disease, such as spatial structuring, within-host dynamics, polymorphism in host resistance, host longevity and population size, impose selection on virulence. As disease incidence increases, it becomes particularly important to take into account the implications of infection by multiple parasite strains. Evolutionary epidemic models also identify the potential importance of immune evasion and optimal virulence for the selection of sex in parasites. Thus, merging epidemiology with evolutionary ecology has widespread potential to help us answer evolutionary questions and to guide public health policy.