1. Department of Microbiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
2. Division of Viral Pathogenesis, Beth Israel Hospital, Harvard University, Boston, MA 02215, USA.
3. Department of Infectious Diseases and Microbiology, University of Pittsburgh, Pittsburgh, PA 15261, USA.
4. California Regional Primate Research Center, Davis, CA 95616, USA.
5. Division of Infectious Diseases, Tropical Medicine and AIDS, Academic Hospital, University of Amsterdam, Academic Medical Centre, Amsterdam, 1105 AZ, Netherlands.
6. Departments of Pathology and Medicine, University of California, San Diego, CA 92093, USA.
7. San Diego VA Health Care System, San Diego, CA 92093, USA.
8. Department of Medicine, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
9. Bernhard-Nocht Institute for Tropical Medicine, Hamburg 20359, Germany.
10. Division of Infectious Disease, Northwestern University Medical School, Chicago, IL 60611, USA.