1. a Center for Health Policy , Duke University , Durham , NC , USA
2. b Department of Medicine, Division of Infectious Diseases , University of Alabama at Birmingham , Birmingham , AL , USA
3. c Department of Medicine, Division of Infectious Diseases and International Health , Duke University , Durham , NC , USA
4. d Department of Psychiatry , University of North Carolina at Chapel Hill , Chapel Hill , NC , USA
5. e Department of Community and Family Medicine and Global Health Institute , Duke University , Durham , NC , USA