Molecular epidemiology and evolution of emerging infectious diseases.

Molecular epidemiology is an emerging science. The development of new and rapid protocols to isolate and identify pathogens, coupled with the sophisticated phylogenetic analysis of their gene sequences, is providing a new and fascinating insight into the biology, origin and spread of infectious diseases. In this essay, I describe some of the ways in which the techniques of modern molecular biology and evolution have equipped us to face the challenge of these new infections.