1. Department of Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
2. Division of Infectious Diseases, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
3. Department of Microbiology, National Hospital for Tropical Medicine, Hanoi, Vietnam
4. Center for Research and Training on Substance Abuse-HIV (CREATA-H), Hanoi Medical University, Hanoi, Vietnam
5. Field School of Public Health at UCLA, Los Angeles, California, USA