1Vietnam Research Station, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki-shi, Nagasaki, Japan.
2Department of Virology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
3Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
4Program for Nurturing Global Leaders in Tropical and Emerging Communicable Diseases, Nagasaki University, Nagasaki, Japan.
5Department of Virology, National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.
6School of International Health, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
7Vietnam Research Station, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki-shi, Nagasaki, Japan. rainbow@nagasaki-u.ac.jp.