1. Department of Microbiology, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo, Hokkaido 060–8638, Japan
2. Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, 1–12–4 Sakamoto, Nagasaki 852–8523, Japan
3. Department of Virology II, National Institute of Infectious Diseases, 4–7–1 Gakuen, Musashi-murayama, Tokyo 208–0011, Japan
4. Department of Virology I, National Institute of Infectious Diseases, 1–23–1 Toyama, Shinjuku-ku, Tokyo 162–8640, Japan
5. Mahara Institute of Medical Acarology, 56–3 Korekuni, Aratano, Anan, Tokushima 779–1510, Japan
6. Bach Mai Hospital, 78 Giai Phong Street, Hanoi 844, Vietnam
7. National Institute of Hygiene and Epidemiology, 1 Yersin Street, Hanoi 10000, Vietnam