1. Department of Virology, Medicum, University of Helsinki, Helsinki, Finland
2. Laboratory of Microbiology and Virology, University Hospital Maggiore Della Carità Di Novara, Italy, Piemonte, Novara
3. Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
4. Department of Virology and Immunology, Helsinki University Hospital Diagnostic Center, Helsinki, Finland