1. Viral Zoonoses Research Unit, Department of Virology, Medicum, Haartmaninkatu 3, University of Helsinki, 00029 Helsinki, Finland.
2. Department of Veterinary Biosciences, Faculty of Veterinary Medicine, Agnes Sjöbergin Katu 2, P.O. Box 66, University of Helsinki, 00014 Helsinki, Finland.
3. Virology and Immunology, Diagnostic Center, HUSLAB, Helsinki University Hospital, 00029 Helsinki, Finland.