1. 1Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Agnes Sjöbergin katu 2, 00790, Helsinki, Finland
2. 2Department of Virology, Faculty of Medicine, University of Helsinki, Haartmaninkatu 3, 00290, Helsinki, Finland
3. †Present address: Anna Knuuttila, Fimmic Oy, Helsinki, Finland.