1. Infectious Diseases Section, Veterans Affairs St. Louis Health Care System, St. Louis, MO 63106, USA
2. Division of Infectious Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA
3. Infectious Disease Clinical Research Program, Preventive Medicine and Biostatistics Department, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA
4. Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, MD 20817, USA