1. Department of Global Health, School for Tropical Medicine and Global Health, Nagasaki University, Nagasaki 852-8523, Japan
2. London School of Hygiene and Tropical Medicine, London E4 7RW, UK
3. School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8523, Japan
4. Kenya Medical Research Institute, Nairobi 54840-00200, Kenya