1. Departments of Virology and Veterinary Biosciences, University of Helsinki, Helsinki, Finland
2. Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska institutet, Solna, Sweden
3. Department of Virology and Immunology, Helsinki university hospital, Helsinki, Finland
4. National Institute for Health and Welfare, Helsinki, Finland
5. Department of Virology, University of Turku, Turku, Finland