1. Department of Epidemiology, University of North Carolina Gillings School of Global Public Health, Chapel Hill, North Carolina.
2. Intracellular Pathogens Research Laboratory, Center for Comparative Medicine and Translational Research, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina.
3. Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC and Department of Hospital Epidemiology, UNC Health Care, Chapel Hill, North Carolina.
4. Western University of Health Sciences, College of Veterinary Medicine, Pomona, California.