The father of a Belfast teenager who is suffering from variant CJD has said experts' predictions more people could be affected by the disease than previously thought were "sad, but not surprising".
Jonathan's condition "has stabilised despite doctors' predictions"
Don Simms first realised his son Jonathan, now 19, was unwell in May 2001.
Jonathan, who was a talented youth footballer, was being a little clumsy and had problems balancing - classic early signs of the prions that cause vCJD to damage the brain.
Doctors first thought he had multiple sclerosis. But Jonathan's illness was later confirmed as vCJD. He was given just months to live.
After a court battle, the family finally won permission for him to be given the experimental drug pentosan polysulphate.
Jonathan was given the treatment - which had not yet been tested on humans - in January 2003.
Don Simms says doctors had not been optimistic before the treatment. But he said it led to "small but significant changes," in his son's condition.
He said: "Jonathan is stable, and still alive. Every day is a bonus."
Mr Simms said the news many other people may have to go through the same experience as his family was "sad, but it's not surprising".
A few months after the treatment, he told the BBC: "What I can categorically state is that Jonathan has not got any worse, he in actual fact shows signs of improvement.
"We have never claimed that the drug is a wonder cure, we simply do not know.
"This is why we as family have to be guarded in our optimism. We are not hailing it as a total success but from what we have seen so far we are much encouraged."
While laboratory experiments suggest the drug has the potential to tackle the condition, the drug is controversial because it has only received limited testing in animals.
In January 2003, a tube was inserted into Jonathan's brain to allow a total of 12 infusions, with gradually increasing doses, be given.
However, fears remain that the treatment may cause harm.
Jonathan's progress is being monitored using regular scans checking for the presence of bleeding around the injection site.
The teenager's condition has deteriorated in the months that his father has been campaigning for him to have the treatment.
Jonathan requires round-the-clock care
He now requires round-the-clock care and the disease has severely affected his speech and eyesight.
Latest figures show 142 people in the UK have died from the variant form of CJD so far, with a handful now living with the illness.