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.