Viral Genetics

The subject of viral genetics is very complex as viruses in general exhibit a wide array of genetic diversity, even amongst individual types of virus. Therefore the following is a brief overview of viral genetics covering the main aspects of veterinary interest.

Genetic Mutation
Viruses often undergo spontaneous and random errors during the process of replication. RNA viruses are particularly susceptible to genetic mutation due to the poor error-correction by RNA replication enzymes. Mutations occurring over several generations may account for phenotypic variations, however most point mutations are silent i.e. they do not influence the amino acid composition of the coded proteins.

Viral Recombination
Viral recombination refers to the process whereby genetic material is transferred between different but closely related viruses that have infected the same cell. It is also possible for genetic recombination to occur between the virus and the host cell. Genetic recombination usually occurs in DNA viruses and involves dissociation and re-establishment of covalent bonds within the nucleic acid. An example of why genetic recombination is important in veterinary medicine is the recent outbreak of avian influenza and the associated risk of it combining with another related influenza virus creating a zoonotic risk. There is also evidence to show that the dual infection of pig populations with avian and human influenza viruses can provide conditions for the emergence of new virulent subtypes which can be zoonotic.