“Creutzfeldt-Jakob Disease (CJD) belongs to a family of human and animal diseases known as the transmissible spongiform encephalopathies (TSEs) or prion diseases.  Spongiform refers to the characteristic appearance of infected brains, which become filled with holes until they resemble sponges when examined under a microscope.  CJD is the most common of the known human TSEs.”

National Institute of Neurological Disorders and Stroke.