1. Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care, Boston, Massachusetts
2. now with Department of Infectious Diseases, Lahey Hospital and Medical Center, Burlington, Massachusetts
3. Department of Biostatistics and Epidemiology, University of Massachusetts Amherst School of Public Health and Health Sciences, Amherst
4. Section of Infectious Disease & International Health, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
5. now with Boston University School of Medicine, Boston, Massachusetts
6. Division of General Surgery, University of California, San Francisco
7. Division of Infectious Diseases and the Health Policy Research Institute, University of California Irvine School of Medicine, Irvine