Chapter

Genetic Diversity of RNA Viruses

Volume 176 of the series Current Topics in Microbiology and Immunology pp 75-97

Evolutionary Processes in Influenza Viruses: Divergence, Rapid Evolution, and Stasis

  • O. T. GormanAffiliated withDepartment of Virology and Molecular Biology, St. Jude Children’s Research Hospital
  • , W. J. BeanAffiliated withDepartment of Virology and Molecular Biology, St. Jude Children’s Research Hospital
  • , R. G. WebsterAffiliated withDepartment of Virology and Molecular Biology, St. Jude Children’s Research Hospital

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Abstract

Interspecies transmissions combined with isolation of host species contribute to the evolutionary divergence of viruses because of the separation of host-specific virus gene pools. Barriers to frequent interspecies transmissions maintain the separation of progeny and parent virus gene pools and allow independent evolution of host-specific strains. These barriers may be in the form of infrequent likelihood of transmission because of different ecologies of host species, a lack of infectivity of the virus in new hosts, or interference from established viruses mediated by host immunity. Partitioning of avian influenza virus gene pools can result from geographic separation of waterfowl populations by separation of flyways and breeding and overwintering grounds. This mechanism has been suggested for the divergence of H4 hemagglutinin lineages in avian viruses (Donis et al. 1989). The subdivision of host populations provides a great deal of heterogeneity to virus populations and enhances the maintainence of a large number of virus subtypes.