It is still possible for viruses such as HIV and hepatitis C to be transmitted through the blood supply, the medical director of the Irish Blood Transfusion Service admitted yesterday.
Dr William Murphy said, however, that the risk was small, with the likelihood of it happening put at one in every two million blood donations.
"These are almost invariably from people who have recently acquired the infection. In the case of HIV, it would be among people who acquired infection within the last few days, and within the last month for people with hepatitis C, but their infection may not be detectable even with the tests we have at the moment," he said.
"They would usually be picked up when they returned to donate blood and the recipients of their previous donation would then be traced."
There was a possibility, however, that the person might never return to donate blood, in which case a contaminated donation might not be picked up until its recipient or recipients became ill.
Transmission of HIV and hepatitis C in this way had occurred in the United States, France, Germany, Singapore and Australia, but there had been no instances of it in the Republic or in the UK. However, the possibility was a "constant worry", Dr Murphy said.
Representatives of the IBTS, together with blood bank directors from several EU member-states, are attending a two-day conference at the RDS in Dublin to discuss ways in which the risk of transmission can be minimised by the use of emerging technologies.
"There are a number of new technologies that are in advanced development stages that might reduce the residual risk of transmission of viruses by blood transfusion further than at the moment. They may be able to reduce it close to zero," Dr Murphy said.
The new technology also had the potential to prevent transmission of emerging viruses before blood banks were even aware that they could be transmitted by blood transfusion. These included the West Nile virus, which broke out in the US last summer. Some 21 people had contracted this virus through blood transfusions and two of them had died.
"The problems are that the technologies are themselves toxic. The way they work is they add toxic chemicals into the blood donation. You leave them there for a while, so that they kill any viruses or bacteria that are in the bag, and then you have to extract them, because they are toxic," Dr Murphy said.
"Given the very low risk of virus transmission anyway, we have to make sure that the cure isn't worse than the disease. That is one of the main issues at this conference."