1. Center for Animal Disease Control, University of Miyazaki, Miyazaki, Japan
2. Hokkaido University, Sapporo, Japan
3. National Research Center for the Control and Prevention of Infectious Diseases, Nagasaki University, Nagasaki, Japan
4. Public Welfare and Health Department, Miyazaki Prefecture, Miyazaki, Japan
5. National Institute of Infectious Diseases, Tokyo, Japan