Researchers have identified three basic ways that Creutzfeldt-Jakob disease (CJD) may develop: Iatrogenic CJD. These are cases of CJD related to medical procedures. A small number of people have developed the disease after being exposed to infected human tissue during a medical procedure, such as a cornea or skin transplant, or grafts of dura mater, the membrane that covers the brain.

Some adults have developed CJD decades after receiving injections of contaminated human growth hormone (HGH) derived from human pituitary glands. It was extracted from the pituitary glands of human corpses. Since the mid 1980s, HGH is generally made from genetically engineered synthetic materials, avoiding the risk of contaminated tissue.

Deformed prions are not affected by standard sterilization methods, including heat, radiation, alcohol, benzene and formaldehyde. As a result, a few people have developed CJD after undergoing brain surgery with instruments contaminated by previous use in a person with CJD. Currently, instruments used during brain surgery on a person with suspected CJD are destroyed.

The guidelines on organ donation and the reuse of surgical equipment have been tightened. As a result, cases of iCJD are now extremely rare.

Variant CJD. Variant CJD has been linked primarily to the consumption of beef infected with bovine spongiform encephalopathy (BSE), also known as mad cow disease. However, not everyone who becomes infected with the abnormal prion protein develops vCJD.

In 2000, research concluded that the prion was spread through cattle that were fed meat-and-bone mix containing traces of infected brains or spinal cords. The prion then ended up in processed meat products, such as beef burgers, and entered the human food chain. Strict controls have been in place since then to prevent BSE from entering the human food chain and the use of meat-and-bone mix has since been outlawed.

Some experts believe that the food controls have worked and that further cases of vCJD will continue to decline.

Other experts have warned that people who have died could have had a genetic trait that meant the vCJD affected them more quickly than normal. Other similar infections caused by prions normally take between 15 and 20 years before they become active. These experts argue that many other people could have vCJD, but the symptoms might not begin to show for many years to come.

Can CJD be transmitted from person to person?

In theory, CJD can be transmitted from an affected person to others, but only through an injection or consumption of brain tissue.

It is thought that CJD is not spread through ordinary day-to-day contact with those affected or by airborne droplets, blood contact or sexual contact.

Written by Stephanie Brunner B.A.