1. Division of Infectious Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
2. Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, California, USA
3. Centre for Infectious Diseases Research in Zambia, Lusaka, Zambia
4. Department of International Health, Johns Hopkins University School of Public Health, Baltimore, Maryland, USA
5. Division of Infectious Diseases, University of Alabama, Birmingham, Alabama, USA
6. Division of Epidemiology, University of California, Berkeley, Berkeley, California, USA
7. Department of Medicine, Georgetown University, Washington, D.C., USA