1. Department of Public Health Sciences, University of California Davis, Davis, California, USA.
2. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
3. Department of Obstetrics & Gynecology, David Geffen School of Medicine at UCLA, University of California Los Angeles, Los Angeles, California, USA.
4. UCLA AIDS Institute, University of California Los Angeles, Los Angeles, California, USA.
5. Department of Infectious Diseases and Microbiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
6. Division of Infectious Diseases, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
7. Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA.
8. Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, USA.
9. Department of Epidemiology, UCLA Fielding School of Public Health, University of California, Los Angeles, California, USA.