Rate of evolution and molecular epidemiology of tick-borne encephalitis virus in Europe, including two isolations from the same focus 44 years apart.
Tick-borne encephalitis virus (TBEV) is a member of the family Flaviviridae. It is transmitted by Ixodes spp. ticks in a cycle involving rodents and small mammals. TBEV has three subtypes: European, Siberian and Far Eastern. The virus causes thousands of cases of meningoencephalitis in Europe annually, with an increasing trend. The increase may be attributed to a complex network of elements, including climatic, environmental and socio-economic factors. In an attempt to understand the evolutionary history and dispersal of TBEV, to existing genetic data we add two novel complete ORF sequences of TBEV strains from northern Europe and the completion of the genome of four others. Moreover, we provide a unique measure for the natural rate of evolution of TBEV by studying two isolations from the same forest on an island in Åland archipelago 44 years apart. For all isolates, we analysed the phylogeny, rate of evolution and probable time of radiation of the different TBEV strains. The results show that the two lineages of TBEV in different Ixodes species have evolved independently for approximately 3300 years. Notably, rapid radiation of TBEV-Eur occurred approximately 300 years ago, without the large-scale geographical clustering observed previously for the Siberian subtype. The measurements from the natural rate of evolution correlated with the estimates done by phylogenetic programs, demonstrating their robustness.
Infection Biology Research Program, Department of Virology, Haartman Institute, PO Box 21, FI-00014 University of Helsinki, Helsinki, Finland.
Nathalie Y
NY
Uzcátegui
Infection Biology Research Program, Department of Virology, Haartman Institute, PO Box 21, FI-00014 University of Helsinki, Helsinki, Finland.
Tarja
T
Sironen
Department of Virology, National Institute for Health Development, EE-11619 Tallinn, Estonia.|Center for Microbiological Preparedness, Swedish Institute for Infectious Disease Control, SE-17182 Solna, Sweden.
Irina
I
Golovljova
Infection Biology Research Program, Department of Virology, Haartman Institute, PO Box 21, FI-00014 University of Helsinki, Helsinki, Finland.
Anu E
AE
Jääskeläinen
Department of Virology, Helsinki University Hospital Laboratory (HUSLAB), PO Box 400, FI-00029 HUS, Helsinki, Finland.|Infection Biology Research Program, Department of Virology, Haartman Institute, PO Box 21, FI-00014 University of Helsinki, Helsinki, Finland.
Hannamari
H
Välimaa
Center for Microbiological Preparedness, Swedish Institute for Infectious Disease Control, SE-17182 Solna, Sweden.
Åke
Å
Lundkvist
Infection Biology Research Program, Department of Virology, Haartman Institute, PO Box 21, FI-00014 University of Helsinki, Helsinki, Finland.
Alexander
A
Plyusnin
Department of Virology, Helsinki University Hospital Laboratory (HUSLAB), PO Box 400, FI-00029 HUS, Helsinki, Finland.|Infection Biology Research Program, Department of Virology, Haartman Institute, PO Box 21, FI-00014 University of Helsinki, Helsinki, Finland.
Antti
A
Vaheri
Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, PO Box 66, FI-00014 University of Helsinki, Helsinki, Finland.|Department of Virology, Helsinki University Hospital Laboratory (HUSLAB), PO Box 400, FI-00029 HUS, Helsinki, Finland.|Infection Biology Research Program, Department of Virology, Haartman Institute, PO Box 21, FI-00014 University of Helsinki, Helsinki, Finland.
Olli
O
Vapalahti
D000818:Animals; D001483:Base Sequence; D004669:Encephalitis Viruses, Tick-Borne / Q000235:genetics*; D004675:Encephalitis, Tick-Borne / Q000453:epidemiology / Q000821:virology*; D004957:Estonia / Q000453:epidemiology; D005060:Europe / Q000453:epidemiology; D019143:Evolution, Molecular; D005260:Female; D005387:Finland / Q000453:epidemiology; D014644:Genetic Variation / Q000235:genetics; D006801:Humans; D018884:Ixodes / Q000821:virology; D008297:Male; D051379:Mice; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D010802:Phylogeny