Creutzfeldt-Jakob disease is a rare fatal degenerative disease of the central nervous system. Creutzfeldt-Jakob disease occurs throughout the world at an incidence of one person in a million; however, among certain populations, such as Libyan Jews, rates are somewhat higher. The disease commonly occurs in adults between the ages of 40 and 70, although some young adults have been stricken with the disease. Both men and women are affected equally. The onset of the disease is usually characterised by vague psychiatric or behavioural changes, which are followed within weeks or months by a progressive dementia that is often accompanied by abnormal vision and involuntary movements. There is no known cure for the disease, which is usually fatal within a year of the onset of symptoms.