1. Division of Infectious Diseases, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, Michigan, MI 48109, USA
2. Department of Obstetrics and Gynecology, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, 4800 Alberta Avenue, El Paso, TX 79905, USA
3. Department of Epidemiology and Biostatistics, University of South Florida College of Public Health, Tampa, FL 33612, USA