1. Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;
2. Hospital for Tropical Diseases, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;
3. Division of Epidemiology, Department of Disease Control, Ministry of Public Health, Nonthaburi, Thailand;
4. Department of Disease Control, Institution for Urban Disease Control and Prevention, Ministry of Public Health, Nonthaburi, Thailand;
5. Division of Communicable Diseases, Department of Disease Control, Ministry of Public Health, Nonthaburi, Thailand