A blood test for variant CJD is for the first time being offered to patients from around the UK and some from abroad who are suspected of having what was once known as mad cow disease.
Please wait while this video loads. If it doesn't load after a few seconds you may need to have Adobe Flash installed.
Channel 4 News has learned that a notification has been sent to neurologists around the country from the NHS National Prion Clinic and the Medical Research Council's Prion Unit saying that the blood test is now available. Between five and 10 samples a week are now being sent in from here and other countries where there have been cases of vCJD.
Professor John Collinge, who has been part of the team developing the blood test, said that so far the test had not produced any false positive results - that is, where a test shows there is infection when there is not.
This is a significant step forward in the fight against the disease. Until now the only way of confirming the diagnosis has been through tonsil biopsies during life or after the patient has died and brain samples can be taken.
Channel 4 News has also learned that funding from the Medical Research Council has meant the team has now been able to begin a crucial new phase in assessing the blood test. This involves testing 5,000 anonymous samples from the US, supplied from the American Red Cross. America has low levels of exposure to BSE and the tests will enable the scientists to assess the false positive rate.
This is a significant step forward in the fight against the disease.
Prof Collinge said if they find there are a significant number of false positives then "it will be back to the drawing board."
If, on the other hand, the test works, then the next step will be to screen 50,000 anonymous UK blood donors which would allow the first accurate assessment of how many people in this country are carrying the disease.
Recent studies from tonsil samples show that possibly one in 4,000 people in the UK or 15,000 in total may be infected with the disease, although some tests have put the numbers slightly higher.
The latest figures from the Health Protection Agency show that there have so far been 176 definite or probable cases of vCJD from when it was first detected in humans in 1995 until the end of 2011. Channel 4 News understands that there was a "cluster" of deaths at the end of the year in which four people died.
Variant CJD is a human form of bovine spongiform encephalopathy (BSE) which first emerged in Britain in 1986 as a result of beef offal being fed to cattle. The prions which are responsible for BSE and vCJD were found in the brains, spinal cords and spleens of cows. When the meat was mechanically recovered, and turned into the likes of hamburgers and baby food, the prions entered the human chain.
Variant CJD is a cruel disease which causes a form of dementia, affecting both the brain and nervous system. It has a long incubation period and mainly affects young people. The majority of deaths have been in those in their 20s, although there have been exceptions.
The development of a possible blood test was announced last February in a scientific paper published in The Lancet. Permission has now been given by UCLH, the hospital trust to which Prof Collinge and his team are attached, to start a clinical evaluation in patients in whom a diagnosis of vCJD is suspected.
Currently blood undergoes leukodepletion which involves the removal of the white blood cells. But this does not remove all the prions and there have been several cases of people infected with vCJD after receiving blood products. There have also been cases of people being infected through the use of surgical instruments.
It is understood that a 50-year-old woman died from vCJD within the past few weeks after she received a blood transfusion in 2002 - four years after leukodepletion was introduced.
Professor Collinge told Channel 4 News said that the blood test was "extremely good news".
Click here for other health stories from Channel 4 News
"In principle, it may allow us to find how many people in the population are infected so we can target risk management strategies and ensure the safety of our blood supply," he said.
"It could also enable us to make an earlier diagnosis and as treatments become available it is going to be desperately important to get to patients early before there is extensive damage to the brain."
Christine Lord, whose son Andy died in 2007 from vCJD, told Channel 4 News that the sad thing was that many people thought this disease had gone away.
"The importance of a blood test means we would protect people and prevent future deaths," Ms Lord said.
"Since my son's death I have visited many more young men and women who are dying with vCJD. It continues to kill on a regular basis. My concern as a Mum who has lost her only son is that no other Mum, Dad or family will go through this. The pain is absolutely unbelievable."
Frank Dobson, who was the Health Secretary who introduced leukodepletion, urged the government to provide any necessary future funding.
"Up to now we have been flying blind, applying the precautionary principle. We now need to have extensive trials because we do not know who is carrying it and who is donating blood," he said.
But apart from government backing needed if they are able to go to the next phase and start testing UK blood samples, Professor Collinge said they would also need a commercial company to step in and take over because his laboratory is simply not capable of dealing with such large scale samples.
Christine Lord's website is www.justice4andy.com