What is CJD?

CJD, or Creutzfeldt-Jakob Disease, is an infectious and deadly brain disease for which is there is no cure or treatment.

It causes personality change, loss of body function, and eventually death.

It is thought to be caused by rogue proteins called prions.

It is a member of the same class of diseases as Bovine Spongiform Encephalopathy (BSE), commonly known as Mad Cow Disease.

Are there different forms of the disease?

There are two forms of CJD, classical and a new form, variant (vCJD).

Three types of classical CJD are recognized: sporadic, familial and iatrogenic.

Sporadic CJD, which comprises 85-90% of all classical CJD cases, occurs spontaneously in the general population with no known cause or triggering event. It is thought that it is this type of the disease with which the hospital patient was infected.

vCJD is a simlar neuro-degenerative disease, but generally occurs in younger people.

Scientists believe vCJD is caused by eating meat infected with BSE.

How widespread is it?

There are about 35 to 70 cases of CJD each year in the UK. Most are of the sporadic form. In total, 117 people in the UK have died from vCJD.

Is there a test?

There is no simple way to diagnose CJD, particularly in its early stages.

However, it may even be infectious before the patient has developed any symptoms.

The disease has a very long incubation period, and so unfortunately the Middlesborough patients may have to wait years before they find out whether or not they are in the clear.

Is there a risk of transmitting the disease during surgery?

Nobody knows for sure, although some experts believe there is a very small risk that the infective agent could be passed via contaminated instruments used during surgery.

Prions are tiny particles that can attach themselves to equipment, and resist attempts to remove them by sterilisation or scrubbing.

There have been five documented cases world-wide of patents developing CJD following surgery with contaminated instruments.

Forty people in the UK have died since 1990 from sporadic CJD as a result of surgical procedures.

However, most had been given accidentally contaminated human growth hormone, and a few had been given infected tissue to repair protective membranes around their brains.

How big is the risk?

The exact risk for each patient depends on the type of operation they had, and which instruments were used by the surgeons.

It is thought that operations on the brain and the tonsils pose the highest potential risk. Prions are also thought to lurk in other tissues, such as the spleen, appendix, intestines and back of the eye.

It is thought that the risk of contamination drops with every new patient the instrument is subsequently used on. After the first six patients the risk is tiny, and some believe it has all but gone after ten.

What safety measures are in place?

The government introduced tight guidelines demanding improved hygiene and sterilisation of surgical instruments in hospitals three years ago following the emergence of vCJD.

The guidance states that if there is a known risk of CJD with a patient then any instruments should be quarantined until the disease is either confirmed or eliminated.

If the diagnosis is postive, the equipment must be destroyed.

What happened at Middlesborough?

The hospital says that the patient was not suspected of having CJD.

If that had been the case, then the surgical instruments would have been immediately quarantined.

CJD was only uncovered following a precautionary test, and the hospital said it was "completely unexpected".

Critics say the hospital should have taken greater care.