[1] Johns Hopkins Univ, Sch Med, Baltimore, MD 21218 USA
[2] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Epidemiol, Baltimore, MD USA
[3] Univ Calif San Diego, Sch Med, San Diego, CA 92103 USA
[4] Univ Washington, Sch Med, Seattle, WA USA
[5] Univ Calif San Francisco, Sch Med, San Francisco, CA USA
[6] Univ Alabama Birmingham, Sch Med, Birmingham, AL USA
[7] Harvard Univ, Sch Med, Cambridge, MA 02138 USA
[8] Univ N Carolina, Gillings Sch Global Publ Hlth, Dept Epidemiol, Chapel Hill, NC 27515 USA