[1] CDC, Atlanta, GA 30333 USA
[2] Calif Pacific Med Ctr, Res Inst, San Francisco, CA USA
[3] Univ Minnesota, Minneapolis, MN 55455 USA
[4] Minneapolis VA Hlth Care Syst, Minneapolis, MN USA
[5] Minneapolis VA Hlth Care Syst, Minneapolis, MN USA
[6] Univ Maryland, Sch Med, College Pk, MD 20742 USA
[7] Univ Pittsburgh, Grad Sch Publ Hlth, Pittsburgh, PA 15260 USA