Doctoral student in epidemiology and a researcher with the Center for Public Health Preparedness and Research, Rollins School of Public Health, Emory University, Atlanta, GA. (Silk)

Rollins Chair and Director, Center for Public Health Preparedness and Research, Rollins School of Public Health, Emory University, Atlanta, GA. (Berkelman)

Corresponding author: Benjamin J. Silk, MPH, Department of Epidemiology, Rollins School of Public Health, 1518 Clifton Rd NE, Atlanta, GA 30322 (e-mail: [email protected]).

This work was made possible through the support of the O. Wayne Rollins Foundation.

The authors thank Dr Jim Buehler for his thoughtful review of this manuscript.