Virus evolution is a subfield of evolutionary biology that is specifically concerned with the evolution of viruses. Many viruses, in particular RNA viruses, have fairly high mutation rates (on the order of one point mutation or more per genome per round of replication in RNA viruses) and short generation times. As a consequence, many viruses can adapt to changes in their environment within months. Virus evolution is an important aspect of the epidemiology of viral diseases such as influenza, HIV, hepatitis, and many others. It also causes problems in the development of successful antiviral drugs, as resistant mutations often appear within weeks to 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 virus evolution is the quasispecies model.