Many more people could become infected with vCJD than previously thought, experts have warned.
The man received blood from a vCJD victim
It follows analysis of a probable transmission of the human form of BSE, via a blood transfusion.
CJD Surveillance Unit scientists found the patient's genetic make-up differed from that of any other person so far diagnosed with the disease.
This suggests that wider groups of people could be at risk than was thought, they write in the Lancet.
Professor James Ironside, who led the research, told BBC News Online that just over half of the population were in the same genetic subgroup as the transfusion patient.
He said the incubation period for the disease could be longer for this group, and it could also mean they were carrying the disease without being aware of it - but still potentially infecting others via blood transfusions or surgical instruments.
The elderly patient, who received a blood transfusion from someone later diagnosed with vCJD in 1999, died five years ago from a ruptured aortic aneurysm.
Variant CJD or vCJD is the human form of BSE It first emerged in 1995 and has so far claimed 142 lives in the UK
The disease, which affects the brain, is believed to have passed from cattle to humans through meat infected with the disease BSE
Although there is ongoing research into potential treatments, there is currently no cure for the disease. Measures have been introduced to restrict the spread of vCJD
Rules ensure BSE infected meat does not enter the UK food chain
And people who have received blood donated by people later diagnosed with vCJD have been banned from donating themselves There were no indications while he was alive that he had a neurological disorder, although a post mortem revealed the vCJD prion in his spleen and lymph nodes.
CJD Surveillance Unit scientists said it was "very likely indeed" that the infection had been acquired from a blood transfusion.
The scientists looked at the patient's genetic make-up.
Everybody has two copies of each gene. The team found that the man had two different versions of a gene which controls the behaviour of healthy prion proteins found in the body. Faulty prions are thought to be the cause of vCJD.
All other victims of the disease who have been examined have had matching versions of the gene, so it was thought that people in this group - who make up around 37% of the population, were susceptible to the disease.
However, scientists say this case shows that people who have unmatching genes are also at risk. Just over half the population fall into this category.
Professor Ironside said: "We have seen the rate of increase in the number of cases of vCJD decline over recent years, but this suggests we should expect to see other cases of vCJD in the future on a longer time-scale.
"We don't know for sure how many people will be affected, but this demonstrates that these individuals are susceptible to vCJD."
But he added: "It's absolutely possible that there may be a new epidemic, because the cases we've seen so far may only be those who are unusually susceptible or have the shortest incubation periods.
"I'm not in the business of scaremongering, but quite clearly the idea that this problem is on the way out is unfortunately not the case at all."
Professor John Collinge, head of the Medical Research Council's prion unit told BBC Radio 4's Today programme he backed Professor Ironside's findings.
He added: "There is considerable uncertainty over how this will unfold.
"But we have to be prepared for it to unfold over decades and not years."
Frances Hall, secretary of the Human BSE Foundation, whose son Peter died from the illness in 1996, said: "The hope was that only those of an unusual genetic type would develop vCJD. Unfortunately it now looks like more people could be susceptible.
"It's still too early in the day to know how many people will eventually end up with this disease.
"The belief is that people with a different genetic make up might take longer to develop the illness, and many more people could eventually get it, which is very frightening indeed."
There is currently no blood test available which can detect if someone is carrying vCJD, although researchers are working to develop one.
The first person to be diagnosed with vCJD after receiving a blood transfusion was revealed last year. That case prompted an investigation which identified 17 living individuals who had received blood components from donors who succumbed to vCJD.
After the second case came to light, the Department of Health said it was extending measures to limit the number of blood transfusions recipients who can become donors.