Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, , 615 N. Wolfe Street, Baltimore, MD 21205, USA. ahassoo1@jhu.edu. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, , 615 N. Wolfe Street, Baltimore, MD 21205, USA. edonnell@jhmi.edu. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, , 615 N. Wolfe Street, Baltimore, MD 21205, USA. ermiller@jhmi.edu. Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, 5001 El Paso Drive, El Paso, TX 79905, USA. zeni.crisp@ttuhsc.edu. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, , 615 N. Wolfe Street, Baltimore, MD 21205, USA. lappel@jhmi.edu.