1. Los Angeles County Department of Health Services, Los Angeles, California, USA
2. Department of Pulmonary and Critical Care Medicine, Yale University, New Haven, Connecticut, USA
3. Department of Medicine, Cambridge Health Alliance, Cambridge, Massachusetts, USA
4. Department of Medicine, University of California, San Francisco, California, USA
5. Department of Medicine, School of Medicine, Loma Linda University, Loma Linda, California, USA
6. Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA
7. Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA