[1] Boston Univ, Ctr Int Hlth & Dev, Boston, MA 02215 USA
[2] Boston Univ, Sch Publ Hlth, Dept Int Hlth, Boston, MA 02215 USA
[3] Boston Univ, Sch Med, Dept Med, Infect Dis Sect, Boston, MA 02215 USA
[4] Ditan Hosp, Dept STDs & Dermatol, Beijing, Peoples R China
[5] Horizon Res Grp, Beijing, Peoples R China
[6] Tufts Univ New England Med Ctr, Inst Clin Res & Hlth Policy Studies, Boston, MA USA