1. Duke Clinical Research Institute, Duke University School of Medicine , Durham, North Carolina , USA
2. Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic , Rochester, Minnesota , USA
3. Biostatistics Center , Department of Biostatistics and Bioinformatics, George Washington University, Rockville, Maryland , USA
4. Division of Infectious Diseases, Department of Medicine, University of California , San Francisco, California , USA
5. Division of Infectious Diseases, Department of Medicine, Duke University School of Medicine , Durham, North Carolina , USA
6. Division of Public Health, Infectious Diseases, and Occupational Medicine, Department of Medicine, Mayo Clinic , Rochester, Minnesota , USA