The first case to originate in the Republic of Ireland of the human form of mad cow disease has been confirmed.
One variant CJD case has previously been diagnosed in Ireland
A man believed to be in his early 20s is seriously ill in a Dublin hospital with fatal brain disease variant CJD.
The hospital said in a statement that the result of a specialised test made it "most unlikely" that the diagnosis was anything other than vCJD.
It said: "All of the necessary precautions are being taken and the relevant authorities have been updated.
"In the public interest, the hospital reiterates that the patient never received a blood transfusion or made a blood donation, and that the cause of infection is not linked to an operation."
It is understood the man has not lived in Britain, meaning that this is the first case of variant CJD to originate in Ireland.
Neither he nor the hospital are being named to protect the privacy of the man and his family.
Only one variant CJD case has previously been diagnosed in the Irish Republic - a woman who had lived for some time in England.
The hospital confirmed the conclusive test involved a biopsy of the patient's tonsils.
"In the interests of patient confidentiality, further information on the patient's condition will not be issued and we ask that the privacy of the patient and family be respected during this difficult time," the statement added.
Creutzfeldt-Jakob disease (CJD) is one of a small group of fatal diseases caused by infectious agents called prions, which attack the brain.
New variant CJD (vCJD) is caused by exposure to bovine spongiform encephalopathy (BSE) and typically affects younger people.
The Republic of Ireland already has strict restrictions on people who lived Britain between 1980 and 1996 from donating blood.
Contaminated beef was the cause of most cases in the UK, but transfusion experts believe there is a potential for vCJD to be transmitted through blood or blood products.
The Irish Blood Transfusion Service (IBTS) recently announced new donor controls to reduce the risk of vCJD transmission in the country.