1. Department of Virology, National Institute of Hygiene and Epidemiology, 1 Yersin Street, Hanoi, Vietnam
2. Department of Virology, Institute of Tropical Medicine, Nagasaki University, Sakamoto 1-12-4, Nagasaki City 852-8523, Japan
3. Division of Epidemiology, Department of Infectious Diseases, Oita Medical University, Hasama-machi, Oita, Japan
4. Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Sakamoto 1-12-4, Nagasaki, Japan
5. Department of Epidemiology, Entomology Laboratory, National Institute of Hygiene and Epidemiology, 1 Yersin Street, Hanoi, Vietnam
6. CREST, Japan Science and Technology Corporation, Saitama 332-0012, Japan