1. Department of Virology; Institute for Medical Microbiology and Hygiene, University of Freiburg; Hermann-Herder-Strasse 11 79104 Freiburg Germany
2. Laboratory of Public Health, Department of Environmental Veterinary Sciences; Graduate School of Veterinary Medicine, Hokkaido University; Kita-ku, Kita-18, Nishi-9 060-0818 Sapporo Japan
3. Blood Transfusion Service and Internal Medicine; Kumamoto University School of Medicine; Honjo 1-1-1 Kumamoto 860-8556 Japan