1. Department of Emergency Medicine Hakodate Municipal Hospital Hakodate Japan
2. Department of Gastroenterology Hakodate Municipal Hospital Hakodate Japan
3. Department of Emergency Medicine Sapporo Medical University School of Medicine Sapporo Japan
4. Department of Hygiene Sapporo Medical University School of Medicine Sapporo Japan
5. Department of Veterinary Medicine National Institute of Infectious Diseases Tokyo Japan