Lyme disease is caused by a bacterium called Borreliaburgdorferi. It is known as a spirochete because of its long, corkscrew shape. This photograph shows the typical corkscrew appearance of a spirochete. (Image courtesy of the Centers for Disease Control and Prevention.)
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.