Health Secretary John Reid told Parliament it was not possible to determine whether the transfusion recipient contracted the fatal brain-wasting illness from the donor or whether the two were independently infected. But it was the first report supporting the idea the disease might be transmitted through blood transfusions.
"This is a single incident, so it is impossible to be sure which was the route of infection. However, the possibility of this being transfusion-related cannot be discounted," he said.
Dr. Philip Tierno, director of clinical microbiology and immunology at New York University Medical Center said experts have long suspected the disease, variant Creutzfeldt-Jakob disease, might be spread through blood transfusions. Animal studies have indicated it's possible and have suggested that white blood cells could be a source of infection, he said.
Britain has already put in place extra precautions on the blood supply in case that turns out to be true.
However, the transfusion reported Wednesday occurred in 1996, one year before the government started to apply such safeguards to the blood supply in Britain, where nearly all cases have developed. All blood products for use in operations in Britain are now based on plasma imported from the United States, where there have been no cases of human mad cow disease blamed on American beef.
The donor had shown no signs of variant CJD when giving blood in March 1996. Soon afterward, the blood was given to the recipient during an operation for a serious illness. The donor developed the disease in 1999 and died, Reid said.
The recipient of the blood transfusion died this autumn and a post mortem confirmed variant CJD.
"It is therefore possible that the disease was transmitted from donor to recipient by blood transfusion," Reid told lawmakers. "This is a possibility, not a proven causal connection."
Tierno said there was no cause for panic. The number of infections is low, strong controls are now in place and it seems it may take more than just exposure to infected beef to trigger the infection, he said, noting that research has indicated a genetic anomaly appears to play a role.
"It may very well be a red herring that the person got blood, but then again it causes us to think very carefully," Tierno said.
The link between the blood donor and the recipient was first reported to health department officials last week, at which time doctors had yet to confirm the recipient had the disease.
Reid said 15 people in Britain have received blood donations from people who have gone on to develop variant Creutzfeldt-Jakob disease. All of them were being contacted by officials and offered counseling, he said.
There is no blood test to screen for variant CJD, but precautions in Britain and abroad have been in place since 1997.
Since 1997, the National Blood Service donor records are checked every time a new case of variant CJD has been identified and if the victim has given blood, all stocks from that donor are destroyed.
Further measures to remove most of the white cells from blood destined for transfusion were introduced in 1998. The process, called leuco-depletion, was a precautionary move because white blood cells were seen as a theoretical source of infection.
Later in 1998, the government announced it would phase out the use of British plasma in the manufacture of blood products. Since 1999, all blood products have been made using plasma imported from the United States.
Reid said an expert committee on the safety of blood and tissues has been asked to look at whether further precautionary measures should be taken.
The American Red Cross guidelines ban donations from anyone who has been in Britain for more than three months since 1980.
Twelve other countries have banned blood donations from anyone who has visited or lived in Britain for six months or more during the most dangerous period — between 1980 and 1996, according to Britain's Department of Health. Those countries are: Australia, Austria, Canada, Finland, France, Germany, Hong Kong, Israel, Italy, Japan, New Zealand and Switzerland.
Scientists believe variant CJD comes from eating products from cows infected with a similar illness, bovine spongiform encephalopathy, also known as mad cow disease.
Cattle were infected in the late 1980s and early 1990s in Britain after they were fed meat and bone meal from infected animals. Since then, cases have been reported in many other countries, from Europe to Asia. Experts believe the disease was spread through exports of infected animals and meat products.
The human form of mad cow disease so far has claimed 143 victims in Britain and 10 elsewhere.
Three cases of variant CJD — one each in Ireland, Canada and the United States — occurred in people who had lived in or visited Britain at the height of the mad cow disease epidemic. The other seven — six in France and one in Italy — occurred in people who had not been to Britain.