CJD is a progressive, often fatal slow virus (or prion) disease
of the central nerv system; symptoms include progressive dementia
and myoclonic seizures. It mostly affects middle-aged adults but
there are exceptions. Human to human transmission has been known
to occur when dura mater from cadavers have been transplated and by
application of previously contaminated internal brain electrodes
(EEG). Many patients ending up with CJD have a history of some
invasive neurological procedurd.
The disease also occurred in patients who were treated with human
growth hormone prepared from cadaver pituitary glands.
The infectious agent is similar to the organism which causes
scrapie in sheep and is a primitive type of virus particle
referred to by some as a "prion."