Many viral pathogens, especially those with an RNA genome, are characterized by their high mutation rates and large population sizes. These features are responsible for the high levels of genetic variation usually found in viral populations and for their rapid response to different selective challenges encountered during their infection and transmission processes. They are quantitatively and qualitatively so different from most other organisms that special models and concepts, such as the quasispecies model, have been developed to better describe the evolutionary dynamics of viral populations (Xu, 2010).

Population genetics theory provides an adequate frame-work for analyzing and interpreting genetic variation in viral populations, for understanding their dynamics, and to study adaptive processes occurring therein. However, not all the evolutionary changes observed are due to the action of positive selection and this is not an all-mighty agent of evolutionary change. A recently developed framework is being utilized for integrating the evolutionary and epidemic behavior of infectious organisms, known as phylodynamics, which is especially well-suited for fast evolving organisms such as viruses (Xu, 2010).

References:
Xu, J. (2010) Microbial Population Genetics. Caister Academic Press, Norfolk, UK.

Recommended reading:
Virology publications

Labels: Phylodynamics, population genetics, Viral Pathogens