Different types of fleas prefer specific animals as hosts, but will infest humans if their specific hosts are unavailable. Fleas can carry plague and typhus. They are also thought to transmit several other diseases. (Image courtesy of the Centers for Disease Control and Prevention.)
Review Date 6/20/2021
Updated by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.