THE EVOLUTION OF PARASITIC DISEASES

Parasites are characterized by their fitness-reducing effect on their hosts. Studying the evolution of parasitic diseases is an attempt to u nderstand these negative effects as an adaptation of the parasite, the host, both or neither. Dieter Ebert and E. Allen Herre here discuss h ow the underlying concepts are general and are applicable for all type s of disease-producing organisms, broadly defined here as parasites. T he evolutionary processes that lead to the maintenance of the harmful effects are believed to be characterized by genetic correlations with other fitness components of the parasite. Depending on the shape of th ese correlations, any level of virulence can evolve.