1 Department of Medicine, UNC School of Medicine, University of North Carolina, Chapel Hill, North Carolina. jabaron@med.unc.edu.
2 Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina.
3 Department of Epidemiology, Geisel School of Medicine at Dartmouth, Dartmouth College, Lebanon, New Hampshire.
4 Department of Veterinary Physiology & Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas.