1Research Institute for Health Sciences, Chiang Mai University, Chiang Mai, Thailand and Henry M. Jackson Foundation, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
2Royal Thai Army Component, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand and Department of Pediatrics, Pramongkuklao Hospital School of Medicine, Bangkok Thailand
3Royal Thai Army Component, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
4Henry M. Jackson Foundation, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
5Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205.
6Faculty of Medicine, Chiang Mai University, Thailand
7Northern Drug Dependence Treatment Center, Chiang Mai, Thailand
8Henry M. Jackson Foundation, Rockville, Maryland 20850
9U.S. Army Medical Component, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
10Henry M. Jackson Foundation, Rockville, Maryland 20850 and Walter Reed Army Institute of Research, Rockville, Maryland 20850
11Research Institute for Health Sciences, Chiang Mai University, Chiang Mai, Thailand
12Henry M. Jackson Foundation, Rockville, Maryland 20850 and Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205