1. Department of Disease Control, Ministry of Public Health, Institute for Urban Disease Control and Prevention, Bangkok, Thailand;
2. Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;
3. Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;
4. Queen Saovabha Memorial Institute, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand