[1] Johns Hopkins Univ, Dept Epidemiol, Bloomberg Sch Publ Hlth, Baltimore, MD USA
[2] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Pediat Adolescent Maternal AIDS Branch, NIH, Bethesda, MD USA
[3] Northrop Grumman Inc, Atlanta, GA USA
[4] Ctr Dis Control & Prevent, Atlanta, GA USA