1. Public Health Sciences Division, Fred Hutchinson Cancer Center, Seattle, Washington
2. Department of Global Health, University of Washington, Seattle
3. Department of Epidemiology, University of Washington, Seattle
4. Center for Clinical Research, Kenya Medical Research Institute, Nairobi, Kenya
5. Department of Medicine, University of Washington, Seattle
6. now with Gilead Sciences, Foster City, California
7. School of Public Health, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya