Why, so far, have epidemics always eventually petered out? Quasispecies theory suggests a (testable!) answer.

In this paper, it is argued that the fact that, so far, even the worst and most far-reaching epidemics-from the Plague of Athens in 430 BC and the Plague of Justinian in 541/542 AD to the Hong Kong Flu from 1968/69-always finally petered out can be explained using Manfred Eigen's quasispecies concept: Indeed, as the infectious agents, while duplicating themselves in the infected organisms, mutate all the time, these infected organisms carry along quite a multitude of mutational variants or-in Manfred Eigen's terms-a whole quasispecies of infectious agents implying that, within that quasispecies, those variants that differ from the wild type may actually serve as some kind of vaccination program when infecting some previously uninfected persons. In this context, some data regarding various recent epidemics will also be illustrated, using Daniel Huson's SplitsTree software tool.