1. Institut für Virologie, Freie Universität Berlin, Berlin, Germany.
2. Department of Infectious Diseases and Respiratory Medicine, Charité, Universitätsmedizin Berlin, Berlin, Germany.
3. Institut für Tierpathologie, Freie Universität Berlin, Berlin, Germany.
4. Institute of Virology and Immunology, Bern and Mittelhäusern, Switzerland.
5. Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
6. Graduate School for Biomedical Science, University of Bern, Bern, Switzerland.
7. Department of Infectious Diseases and Public Health, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong.