Phylogeny of the Simbu serogroup of the genus Bunyavirus

The Simbu serogroup of the genus Bunyavirus, family Bunyaviridae contains 2 5 viruses. Previous serological studies provided important information rega rding some but not all of the relationships among Simbu serogroup viruses. This report describes the nucleotide sequence determination of the nucleoca psid (N) gene of the small genomic segment of 14 Simbu serogroup viruses an d partial nucleotide sequence determination of the G2 glycoprotein-coding r egion (encoded by the medium RNA segment) of 19 viruses. The overall phylog eny of the Simbu serogroup inferred from analyses of the IN gene was simila r to that inferred from analyses of the G2 protein-coding region. Both anal yses revealed that the Simbu serogroup viruses have evolved into at least f ive major phylogenetic lineages. In general, these phylogenetic lineages we re consistent with the previous serological data, but provided a more detai led understanding of the relatedness amongst many viruses. In comparison to previous phylogenetic studies on the California and Bunyamwera serogroups of the Bunyavirus genus, the Simbu serogroup displays much larger genetic v ariation in the N gene (up to 40% amino acid sequence divergence).