SAMRC/Wits Developmental Pathways for Health Research Unit, School of Clinical Medicine, University of the Witwatersrand, Johannesburg, South Africa

Division of Infectious Diseases, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232

Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, 37232

Department of Obstetrics and Gynecology, Vanderbilt University Medical Center, Nashville, TN, 37232