Can mutation and selection explain virulence in human <it>P. falciparum </it>infections?

Abstract Background Parasites incur periodic mutations which must ultimately be eliminated to maintain their genetic integrity. Methods It is hypothesised that these mutations are eliminated not by the conventional mechanisms of competition between parasites in different hosts but primarily by competition between parasites within the same infection. Results This process is enhanced by the production of a large number of parasites within individual infections, and this may significantly contribute to parasitic virulence. Conclusions Several features of the most virulent human malaria parasite Plasmodium falciparum can usefully be re-interpreted in this light and lend support to this interpretation. More generally, it constitutes a novel explanation for the evolution of virulence in a wider range of microparasites.