[1] Massachusetts Gen Hosp, Infect Dis Unit, Charlestown, MA 02129 USA
[2] Harvard Univ, Sch Med, Boston, MA 02114 USA
[3] Dept Publ Hlth, AIDS Off, San Francisco, CA 94140 USA
[4] Massachusetts Gen Hosp, Partners AIDS Res Ctr, Charlestown, MA 02129 USA