1. Johns Hopkins University School of Nursing, Baltimore, Maryland
2. Department of Microbiology, Howard University, Washington, DC
3. Department of Pediatric Allergy and Immunology, Johns Hopkins University School of Medicine, Baltimore, Maryland
4. Georgetown University Laboratory for Children's Health Promotion, Washington, DC
5. Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine
6. Department of Biostatistics, Howard University, Washington, DC