[1] Univ Calif Los Angeles, Fielding Sch Publ Hlth, Dept Epidemiol, CHS 71 269, Los Angeles, CA 90095 USA
[2] Johns Hopkins Univ, Sch Med, Dept Med, Baltimore, MD 21205 USA
[3] Univ Pittsburg, Dept Med, Pittsburgh, PA USA
[4] Northwestern Univ, Feinberg Sch Med, Div Infect Dis, Chicago, IL 60611 USA
[5] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Epidemiol, Baltimore, MD USA
[6] Univ Calif Los Angeles, Fielding Sch Publ Hlth, Dept Biostat, Los Angeles, CA USA