1. Johns Hopkins School of Nursing, Baltimore, Maryland, USA.
2. Division of General Pediatrics and Adolescent Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
3. Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
4. Public Health Management Corporation, Philadelphia, Pennsylvania, USA.
5. Whitman Walker Health, Washington, District of Columbia, USA.
6. Children's National Hospital, Washington, District of Columbia, USA.
7. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.