In the conventional sense, it is not an infectious disease like influenza, herpes or AIDS. In the 1970's, a few cases of CJD occurred in people who contracted the disease after receiving corneal or other transplants from a donor with the disease. Similarly, three cases occurred in people who had undergone brain surgery where someone with CJD had been operated on earlier in the same day with the same surgical instruments. It is now standard practice for all instruments used during an operation on patients with CJD to be destroyed, since it is impossible to be sure that any sterilization method has removed all traces of infection. (There is no evidence that blood transfusions present a risk of CJD transmission).
In 1985 the first case of CJD was reported in a recipient of contaminated human growth hormone (HGH). Since the 1960's, this hormone had been given to children who were unable to manufacture it themselves and who would have otherwise experienced dwarfism. The original source of the material was from the pituitary glands of human cadavers - corpses donated for medical research. Most of the donors were elderly and the fact that batches of the hormone were made from pooled tissue from many donors increased the chances of contamination. Tragically, over 60 HGH-related cases have been discovered world-wide in addition to 4 cases associated with another human-derived hormone, gonadotrophin. HGH manufactured from the cloned human gene became available in the late 1980's. This is entirely free from the risk of infection and the use of pituitary-derived hormone was stopped. However, the incubation period for the development of CJD from this source was 13 years and so the last cases have only recently been diagnosed.
