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Published November 1, 2001 | Published
Journal Article Open

Evolutionary Relationships and Systematics of the Alphaviruses


Partial E1 envelope glycoprotein gene sequences and complete structural polyprotein sequences were used to compare divergence and construct phylogenetic trees for the genus Alphavirus. Tree topologies indicated that the mosquito-borne alphaviruses could have arisen in either the Old or the New World, with at least two transoceanic introductions to account for their current distribution. The time frame for alphavirus diversification could not be estimated because maximum-likelihood analyses indicated that the nucleotide substitution rate varies considerably across sites within the genome. While most trees showed evolutionary relationships consistent with current antigenic complexes and species, several changes to the current classification are proposed. The recently identified fish alphaviruses salmon pancreas disease virus and sleeping disease virus appear to be variants or subtypes of a new alphavirus species. Southern elephant seal virus is also a new alphavirus distantly related to all of the others analyzed. Tonate virus and Venezuelan equine encephalitis virus strain 78V3531 also appear to be distinct alphavirus species based on genetic, antigenic, and ecological criteria. Trocara virus, isolated from mosquitoes in Brazil and Peru, also represents a new species and probably a new alphavirus complex.

Additional Information

Copyright © 2001, American Society for Microbiology. Received 1 May 2001/Accepted 8 August 2001 We thank Robert Tesh, Robert Shope, and Hilda Guzman for providing some of the alphaviruses used in our analyses. A.M.P. was supported by the James W. McLaughlin Fellowship Fund and NIH T32 Training Grant on Emerging and Reemerging Infectious Diseases AI-07536. A.C.B. was supported by a James L. McLaughlin Infection and Immunity Fellowship and NIH Emerging Tropical Diseases T32 training grant AI-107526. This research was supported by National Institutes of Health grants AI-10984 to Robert Tesh, AI-39800 to S.C.W., and AI-10793 to J.H.S. and E.G.S.

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