Distribution and genetic heterogeneity of Puumala virus in Sweden

1 Swedish Institute for Infectious Disease Control, S-105 21 Stockholm, Sweden 2 Microbiology and Tumour Biology Centre, Karolinska Institute, S-171 77 Stockholm, Sweden 3 Department of Genetics, Uppsala University, S-750 07 Uppsala, Sweden 4 Department of Virology, Haartman Institute, University of Helsinki, FIN-00014 Helsinki, Finland 5 Department of Animal Ecology, Umeå University, S-901 87 Umeå, Sweden 6 National Defence Research Establishment, FOA-4, S-901 82 Umeå, Sweden Small mammals trapped in Sweden were analysed for specific antibody responses against three hantavirus serotypes and for the presence of viral antigen. To determine the genetic identity of viral RNA in lungs of seropositive bank voles ( Clethrionomys glareolus ), polymerase chain reactions and subsequent partial sequencing of both the M and S segments were employed. The sequences obtained were all identified as Puumala (PUU) virus, with a high degree of heterogeneity between the different geographical localities. Alignment of nucleotide and deduced amino acid sequences, together with phylogenetic analysis, showed that PUU viruses circulating in central Sweden were distinct from those in the northern region. The localization of the two distinct PUU virus genotypes was shown to correlate with the postglacial recolonization of Sweden by bank voles. Received 2 February 1996; accepted 4 June 1996.