One strain, nvCJD, is linked to Mad Cow Disease in England. We have classical CJD in the United States and throughout the world. The cause of most cases of CJD is unknown. The incubation period can be decades. CJD should be considered whenever a person develops a rapid dementia and involuntary, irregular jerking movements.
Initial symptoms are often psychological, visual and coordination problems.
The person usually dies within a year of showing symptoms. It is not known if CJD is spread to humans by blood. The infectious agent has been found in blood, but there have been no documented cases of people getting CJD through blood products. As a precaution, blood relatives of CJD victims and people who are at risk for CJD due to past medical procedures should not donate blood. The Centers for Disease Control is conducting a study to determine if CJD can be transmitted to humans by blood.