[1] Univ Pittsburgh, Grad Sch Publ Hlth, Infect Dis Epidemiol Res Unit, Pittsburgh, PA 15213 USA
[2] Univ Pittsburgh, Grad Sch Publ Hlth, Dept Epidemiol, Pittsburgh, PA 15213 USA
[3] Univ Pittsburgh, Sch Med, Pittsburgh, PA 15213 USA
[4] Johns Hopkins Univ, Bloomberg Sch Hyg & Publ Hlth, Dept Int Hlth, Baltimore, MD USA
[5] Ctr Dis Control & Prevent, Atlanta, GA USA