Molecular evolution of Puumala hantavirus

Puumala virus (PUUV) is a negative-stranded RNA virus in the genus Hantavir its, family Bunyaviridae. In this study, detailed phylogenetic analysis was performed on 42 complete S segment sequences of PUUV originated from sever al European countries, Russia, and Japan, the largest set available thus fa r for hantaviruses. The results show that PUUV sequences form seven distinc t and well-supported genetic lineages; within these lineages, geographical clustering of genetic variants is observed. The overall phylogeny of PUUV i s star-like, suggesting an early split of genetic lineages. The individual PUUV lineages appear to be independent, with the only exception to this bei ng the Finnish and the Russian lineages that are closely connected to each other. Two strains of PUUV-like virus from Japan form the most ancestral li neage diverging from PUUV. Recombination points within the S segment were s earched for and evidence for intralineage recombination events was seen In the Finnish, Russian, Danish, and Belgian lineages of PUUV. Molecular clock analysis showed that PUUV is a stable virus, evolving slowly at a rate of 0.7 X 10(-7) to 2.2 x 10(-6) nt substitutions per site per year.