[1] Fred Hutchinson Canc Res Ctr, Div Human Biol, Seattle, WA 98109 USA
[2] Fred Hutchinson Canc Res Ctr, Dept Publ Hlth Sci, Seattle, WA 98104 USA
[3] Univ Washington, Dept Med, Seattle, WA USA
[4] Univ Washington, Dept Epidemiol, Seattle, WA 98195 USA
[5] Univ Washington, Dept Biostat, Seattle, WA 98195 USA
[6] Coast Provincial Gen Hosp, Mombasa, Kenya
[7] Univ Nairobi, Dept Med Microbiol, Nairobi, Kenya