New Zealand's blood banks plan to reject donors with a record of chronic fatigue syndrome (CFS).
The move follows research overseas which has raised concerns about the potential for a recently identified virus XMRV to spread through blood transfusions.
XMRV is a retrovirus, a kind of virus that inserts its genetic map into the cells it infects - something that can have a variety of effects, including killing the cell or turning it cancerous by affecting its genetic makeup.
It was first detected in prostate cancers in 2006 and has been found in 27 percent of such tumours, especially aggressive tumours.
There is now conflicting evidence surrounding a link to CFS, which is also known as ME in New Zealand where there are reported to be 20,000 sufferers.
Canadian authorities have already imposed a lifetime ban on former CFS patients donating blood.
They took the precautionary step earlier this month, based on US research that showed the retrovirus may be transmissible through infected blood.
Across the Tasman, Australia's Red Cross Blood Service is also reviewing its donation guidelines.
The national medical director for New Zealand blood banks, Peter Flanagan, told NZPA the NZ Blood Service (NZBS) would be adopting a similar approach to that being developed by the Canadian blood services.
The NZBS reviewed the issue at a meeting held earlier this month and decided the present exclusion of blood from people still suffering CFS or patients who had been diagnosed in the past two years "should be extended to also exclude donors who report ever having been diagnosed with chronic fatigue syndrome," he said.
The decision was made despite a lack of good scientific data on the issue, he said.
Of the 97 CFS patients excluded from donation in New Zealand over the past 11 years, 12 have recovered and subsequently donated blood at least once.
New Zealand health officials have known of the potential linkage since at least October last year.
A US study of blood samples taken from 101 people with CFS found 95 per cent also showed evidence of XMRV infection.
CFS was first identified in New Zealand, when West Otago doctor Peter Snow identified what became popularly known as "Tapanui flu". Research he published with two Otago University academics attracted international attention despite scepticism by some elements of the medical profession claiming the severe debilitation was a psychological condition, or "yuppie flu".
After hundreds of Americans in Nevada also developed fatigue and memory problems after suffering flu-like symptoms, the US Centres for Disease Control labelled the illness chronic fatigue syndrome, which led to many patients being labelled as malingerers.
But the identification of the XMRV retrovirus in CFS patients at a private US institute supported the late Dr Snow's initial suspicions the disease was caused by a virus. XMRV was also found in 2006 in some prostate cancer patients.
Researchers are now trying to work out how the virus is transmitted, whether it is the cause of CFS, or an opportunistic infection which triggers other underlying conditions and viruses and how people could be screened for the virus in a simple lab test. If it is confirmed as a cause of CFS, researchers will want to know if it requires an environmental trigger, such as stress, to affect the patient.
There is an anti-HIV drug, Isentress, which was effective against XMRV, according to Utah University researchers.