There are growing fears over the risk that vCJD, the human form of mad cow disease. What is the risk?
vCJD is a fatal brain disease
What is vCJD?
Variant CJD or vCJD is the human form of BSE. It first emerged in 1995 and has so far claimed 158 lives in the UK.
The disease, which affects the brain, is believed to have passed from cattle to humans through infected meat.
It causes personality change, loss of body function, and eventually death. It is thought to be caused by rogue proteins called prions.
Doctors are testing a number of experimental treatments. However, as yet there is no cure.
Why is this blood transfusion case important?
It is known that 66 people received blood donated by someone who went on to develop vCJD. Forty-two have died, three - including this case - of vCJD.
The first case of vCJD transmission by blood transfusion, diagnosed after death, was announced by then Health Secretary John Reid in December 2003. A second case was also diagnosed at post mortem.
But the latest case illustrates that the prions - rogue proteins - that cause vCJD can be incubated for many years before symptoms become apparent.
The patient received a blood transfusion at the age of 23. When he was 31, he was referred to the National Prion Clinic after experiencing balance and concentration problems.
He was diagnosed as having vCJD, which was confirmed after his death at the age of 32.
Are other people at risk?
The 24 people who are known to have received infected blood are thought to be at "substantial risk".
However experts are warning that, because there is no test to pick up vCJD in the blood, other infected samples could be in the donor blood bank.
What can be done?
Professor John Collinge, of the National Prion Clinic, is calling for research investigating the worth of tonsil testing to be concluded quickly.
A study of 12,000 appendix and tonsil samples showed three had signs of vCJD.
The scientists at Derriford Hospital in Plymouth and the National CJD Surveillance Unit in Edinburgh extrapolated the figures for the entire population and calculated that on the basis of this study 3,800 people could be harbouring the disease.
A larger-scale study of 100,000 samples is underway to check if this is a reliable way of detecting if people have vCJD.
Why is there a delay?
While scientists agree there is a need for a test to diagnose vCJD, there were some concerns that the figures from the initial study were not reliable.
One of the problems was that appendix samples do not always show up vCJD prions. Another is that these prions were only found in three samples and then extrapolated.
In addition, scientists don't know at what stage in the disease these prions are found in tissue.
Could we see more cases of vCJD?
That is the fear.
Nevertheless, some experts believe the number of people dying from the disease is levelling out and may even be declining.
At its peak in 2000, the disease killed 28 people. Last year, six people died and so far this year, three deaths have been reported.
What safeguards are in place?
Tight rules have been introduced to ensure that BSE infected meat does not enter the UK food chain.
The focus now is on trying to reduce the risks of one person transmitting the disease to another person.
For instance, white blood cells have been removed from all blood used for transfusions since 1999.
This followed advice that if there was any risk of the disease being transmitted through blood, it was most likely to be found in these cells.
Blood products, such as clotting agents, are now only made using plasma from the United States.
Children born from 1996 onwards now only receive plasma that has been imported from the US.
The government recently banned people who had a blood transfusion after 1980 from donating blood.
It followed reports that one man who died from the disease may have caught it from a transfusion.
The Department of Health is spending £200m on improving its procedures for decontaminating surgical instruments, to reduce any risk of the disease being transmitted in this way.
As yet, there is no clear evidence that vCJD can be transmitted through contaminated blood or surgical instruments.
However, these steps have been taken as a precaution.