About 5 to 10 percent of Creutzfeldt-Jakob disease cases are inherited, manifesting in patients with a mutant copy of a gene controlling the formation of a certain protein in the body, states the NIH. Transmission between individuals requires extremely intimate contact, including exposure to brain tissue or corneal transplantation.
Creutzfeldt-Jakob disease is inevitably fatal but is very rare and has an extremely low level potential for transmission, reports Mayo Clinic. While some patients contracted a variant of CJD in the 1990s that may have been transmitted by cows infected with bovine spongiform encephalopathy, there is no direct proof that the patients contracted the disease by consuming contaminated beef.
Scientists have yet to identify a specific causative agent. The leading theory is that the disease is caused by a prion, a protein that is identical in amino acid sequence to one that occurs naturally but is folded into an unusual conformation and that can infectiously transform other copies of the protein that are folded correctly into the incorrect form, according to the NIH.
The majority of CJD cases are spontaneous and develop for no apparent reason, according to Mayo Clinic. The disease is not transmitted by sexual contact or less intimate contact. There are no documented cases of the disease being transmitted through blood, but it can be transmitted through exposure to human tissue, states the NIH. Patients have contracted the disease through injections of contaminated pituitary growth hormone derived from human pituitary glands, from improperly sterilized surgical instruments, and from direct transplantation of human tissue, such as skin or corneal transplants.