ISOLATION AND CHARACTERIZATION OF PUUMALA HANTAVIRUS FROM NORWAY - EVIDENCE FOR A DISTINCT PHYLOGENETIC SUBLINEAGE

Puumala (PUU) hantavirus is the aetiological agent of nephropathia epi demica (NE), a mild form of haemorrhagic fever with renal syndrome, wh ich occurs in Fennoscandia, central Europe and Russia. In Norway, NE-l ike disease has been reported since 1946 and about 50 cases are diagno sed annually; however, the causative agent has not been characterized. In this study, a virus originating from bank voles (Clethrionomys gla reolus) trapped near the town of Eidsvoll (Akershus county) was isolat ed and passaged in laboratory-bred bank voles, The bank vole strain wa s identified as a PUU virus by serological typing and by sequence anal ysis of the S and M gene segments. For comparison, complete or partial S sequences were determined for wild-type PUU strains from five locat ions in Sweden, two inhabited by the southern variant of bank vole pre sent in Fennoscandia, and three by the northern variant. Phylogenetic analysis showed that Norwegian PUU strains are clustered together with Swedish strains from the first group forming a well-supported subline age within the PUU genotype, distinct from other sublineages from nort hern Sweden, Finland, Russia and France. The results are consistent wi th the view of a complex evolutionary history of PUU strains in post-g lacial Fennoscandia. Analyses of the current collection of nucleotide sequences suggest that PUU is the most variable genotype of the known hantaviruses.