1. Department of Emerging and Infectious Diseases, United States Army Medical Research Directorate–Africa, Kenya Medical Research Institute/Walter Reed Project , Kisumu , Kenya
2. Medical Research Council, Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London , London , United Kingdom
3. Kenya Medical Research Institute , Nairobi , Kenya
4. US Military HIV Research Program, Walter Reed Army Institute of Research , Silver Spring, Maryland , USA
5. Department of Pathology and Area Laboratory Services, Tripler Army Medical Center , Honolulu, Hawaii , USA