1. Department of Pediatric Infectious Diseases, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
2. School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan
3. Department of Pediatrics, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
4. Department of Bacteriology, National Institute of Hygiene and Epidemiology, Hanoi, Vietnam
5. Department of Epidemiology, Pasteur Institute, Nha Trang, Vietnam