[1] Vanderbilt Univ, Sch Med, Ctr Human Genet Res, Nashville, TN 37203 USA
[2] Duke Univ, Sch Med, Durham, NC USA
[3] Gilead Sci Inc, Durham, NC USA
[4] Harvard Univ, Sch Publ Hlth, Boston, MA 02115 USA
[5] Case Western Reserve Univ, Sch Med, Cleveland, OH 44106 USA
[6] Univ Witwatersrand, Johannesburg, South Africa