Prion Disease

Prion diseases or transmissible spongiform encephalopathies (TSEs) are a family of rare progressive neurodegenerative disorders that affect both humans and animals. They are distinguished by long incubation periods, characteristic spongiform changes associated with neuronal loss, and a failure to induce inflammatory response.
The causative agent of TSEs is believed to be a prion. A prion is an abnormal, transmissible agent that is able to induce abnormal folding of normal cellular prion proteins in the brain, leading to brain damage and the characteristics signs and symptoms of the disease. Prion diseases are usually rapidly progressive and always fatal.

In 1957 Kuru was the first human disease identified as a prion disease. Kuru was spread among the Fore tribe people in Papua New Guinea and caused by a ritual cannibalism. Besides the symptomatic coordinative malfunctions the cerebellar deficits were often associated by uncontrollable and inappropiate episodes of laughter, hence Kuru was named "laughing death" by the Fore people.

Creutzfeldt-Jakob Disease (CJD)

Diagnosed independently by Drs. Creutzfeldt and Jakob in the early 1920s, the disease that bears their names is a rare, degenerative brain disorder that affects approximately one person per million per year worldwide. This translates into 250-300 new U.S. cases annually. However, because Creutzfeldt-Jakob Disease (CJD) is very difficult to diagnose, this number may actually be higher. CJD affects men and women of all cultural backgrounds, with symptoms appearing most often in those aged 50 to 75.

Creutzfeldt-Jakob Disease is known as a prion disease, which means that healthy brain tissue deteriorates into an abnormal protein that the body cannot break down. CJD is a type of transmissible spongiform encephalopathy (TSE), a classification that includes both human and animal diseases. "Spongiform" refers to the characteristic appearance of an infected brain, which becomes filled with holes until it looks like a sponge under a microscope.
Prior to the "mad cow disease" epidemic of the 1990s, few people had heard of Creutzfeldt-Jakob Disease. However, once a growing number of young people in the United Kingdom started developing symptoms that appeared congruent with CJD, the world became alarmed. This new form of the illness, named variant Creutzfeldt-Jakob Disease or vCJD, results only from exposure to beef that is contaminated with bovine spongiform encephalopathy (BSE), the scientific term for mad cow disease.

There is not yet a cure for Creutzfeldt-Jakob Disease; only treatment for relieving symptoms. Current clinical trials are testing promising antiviral drugs such as amantadine, which has proved helpful in treating Parkinson's disease. Some patients taking these antivirals have shown brief periods of improvement, with no harmful side effects.

For more information on symptomes, etc:

http://www.helpguide.org/elder/creutzfeldt_jakob.htm