1. Division of Infectious Diseases, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.
2. Department of Biostatistics, University of Alabama at Birmingham, Birmingham, Alabama.
3. Department of Medicine, University of Arkansas, Little Rock, Arkansas.
4. Infectious Diseases Section, Department of Medicine, WG Hefner Medical Center, Salisbury, North Carolina.
5. Infectious Diseases Section, Department of Medicine, Wake Forest University Health Sciences, Winston-Salem, North Carolina.