Viral evolution

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Viral evolution is a subfield of evolutionary biology that is specifically concerned with the evolution of viruses. Many viruses, in particular RNA viruses, have short generation times and relatively high mutation rates (on the order of one point mutation or more per genome per round of replication for RNA viruses). This elevated mutation rate, when combined with natural selection, allows viruses to quickly adapt to changes in their host environment.

Viral evolution is an important aspect of the epidemiology of viral diseases such as influenza, HIV, and hepatitis. It also causes problems in the development of successful vaccines and antiviral drugs, as resistant mutations often appear within weeks or months after the beginning of the treatment.

RNA viruses are also used as a model system to study evolution in the laboratory.

One of the main theoretical models to study viral evolution is the quasispecies model, as the viral quasispecies.

[edit] Inter-host and Intra-host evolution

In evolutionary virology and to an extent in the wider field of pathology, inter-host evolution is considered to represent the geological, i.e. visible or detectable, evolution of a virus while intra-host evolution represents the invisible evolution of a virus. Adaptive changes acquired by inter-host evolution are rarely lost once acquired. Changes acquired by intra-host evolution may be lost if the evolutionary landscape changes, for example: a population of viruses may become resistant to an antiviral drug while the host (patient) takes it, but rapidly revert to wild-type if treatment ceases.

Changes may include point mutations or epistatic mutations, as well as genome rearrangements to genes and other functional gene sequences such as gene acquisition, gene creation and gene deletion as well as recombination and translocation events.

[edit] See also

• Viral classification
• RNA virus
• DNA virus
• Viral quasispecies

[edit] Further reading

• E. Domingo and C.K. Biebricher and M. Eigen and J.J. Holland (2002). Quasispecies and RNA Virus Evolution: Principles and Consequences. Landes Bioscience.
• S.F. Elena and R. E. Lenski (2003). Evolution experiments with microorganisms: the dynamics and genetic bases of adaptation. Nat. Rev. Genet. 4:457-469.