HIV-1 Populations in Semen Arise through Multiple Mechanisms. by Anderson, J, Ping, L, Dibben, O, Jabara, C, Arney, L, Kincer, L, Tang, Y, Hobbs, M, Hoffman, I, Kazembe, P, Jones, C, Borrow, P, Fiscus, S, Cohen, MS, Swanstrom, R