1. Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Division of Global Health Equity, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
2. South African Medical Research Council, Pretoria
3. University of Pretoria, Pretoria, South Africa
4. Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts
5. Centers for Disease Control and Prevention, Atlanta, Georgia, USA