Space, time and persistence of virulent pathogens.

Epidemiological theory predicts that pathogens of high virulence should not become endemic. We show, using an empirically based lattice map model, that a pathogen that is too virulent to persist if its host population is spatially well mixed, can persist if the host population is spatially distributed, because of internally generated complex spatial dynamics, provided that the area occupied by the host population is sufficiently large. The dynamics are not an artefact of spatial or temporal discretization. The results uncover a mechanism for the persistence of virulent pathogens, suggesting a means by which pathogens of high virulence could achieve sustained as well as short-term biological pest control.