Two studies published in The Lancet medical journal in Britain show infection through blood is a possible route of transmission.
The UK had announced last December what it said could be the world's first case of variant Creutzfeldt-Jakob disease (vCJD) spread by transfusion, following the death of an unidentified patient several years after receiving blood from a donor later found to have had the illness.
UK Health Secretary John Reid said at the time it was not certain whether the patient had been infected through the transfusion or by eating meat infected with Mad Cow disease.
But Professor Robert Will of the National CJD Surveillance Unit at Western General Hospital in Edinburgh, Scotland said transfusion could have been the cause.
"Our findings raise the possibility that his infection was transfusion-transmitted," Professor Will said.
Variant CJD is the human equivalent of Bovine Spongiform Encephalopathy (BSE) or Mad Cow disease, an incurable degenerative brain disorder linked to eating meat infected with BSE.
After studying blood donation records and the details of the case, Will and his team said the patient was much older than most vCJD sufferers and the odds of it not being through a transfusion were about one in 15,000-30,000.
In a separate study in the journal, scientists at the department of medical research at the French Atomic Energy Commission found that the macaque monkey can be infected with BSE orally or intravenously.
Based on their findings, they said blood transfusion should be regarded as a "likely route of contamination for vCJD patients with a medical history involving a transfusion during the period of risk."
Up to December 2003, 153 cases of vCJD had been reported worldwide.