[1] Kenya Govt Med Res Ctr, Ctr Clin Res, Thika Project, PHRD, Nairobi, Kenya
[2] Univ Michigan, Sch Publ Hlth, Hlth Behav Hlth Educ, Ann Arbor, MI 48109 USA
[3] Univ Calif San Francisco, Dept Med, Div Prevent Sci, San Francisco, CA 94143 USA
[4] Jomo Kenyatta Univ Agr & Technol, Dept Community Hlth, Juja, Kenya
[5] Univ Calif San Francisco, Dept Med, Div HIV Infect Dis & Global Med, San Francisco, CA 94143 USA