Sporadic Creutzfeldt-Jakob Disease (sCJD)
As noted earlier, sporadic CJD is the most common form of the classical prion diseases. People with this form of CJD develop the disease for no apparent reason. Since cases occur with no explanation, it is referred to as sporadic or spontaneous CJD. It affects both males and females from all cultural backgrounds. The disease appears most often in individuals 50-75 years of age.
Iatrogenic Creutzfeldt-Jakob Disease (iCJD)
Iatrogenic CJD is acquired through a surgical procedure or medical treatment such as contamination from brain surgery, corneal transplants, or grafts of dura mater. This is because surgical instruments were contaminated with prions from prior surgeries and, unlike bacteria, viruses, and fungi, prions are not affected by any standard sterilization methods. The World Health Organization recommends that surgical instruments used on individuals suspected of having CJD be discarded and destroyed by incineration. A rare number of individuals developed iatrogenic CJD after receiving injections of contaminated human growth hormone. Originally the growth hormone was extracted from the pituitary glands of human corpses. Since the mid-1980s, most growth hormone has been genetically engineered from synthetic materials, lessening the risk of infection in this manner. In addition, guidelines for organ donation have been tightened.