April 16, 2010

An AIDS-like virus that has been linked to chronic fatigue syndrome is causing Canadian blood officials to ban anyone who has suffered from the ailment from making donations.

While stressing that researchers have found no definitive links between the virus, known as XMRV, and the chronic fatigue, Canadian Blood Services says they will err on the side of caution and implement the new donation restrictions.

Canada is the first country in the world to make the move, which is being rolled out in donation centres nationwide over the coming weeks, says Dana Devine, head of medical and scientific research with the blood services agency.

"We've basically said ‘okay, let's assume that this might be a problem and let's not wait until all these studies have sorted out the answer,' " Devine says.

"Because we're uncertain of the state of the science still, we're going to wait until this sorts out and defer anyone who's been diagnosed," she says.

The move was given Health Canada approval last month and will be fully in place in the coming two weeks.

U.S. media outlets reported this week that public health authorities there were investigating the possibility that the retrovirus posed a threat to that nation's blood supply.

Because it closely resembles the AIDS virus, many believe XMRV can be similarly transmitted through the exchange of bodily fluids or blood transfusions.

And a study published last October in the prestigious journal Science suggested that XMRV was strongly associated with chronic fatigue.

In the paper, researchers found that many of the 101 study subjects who suffered from the condition also had been infected with the retrovirus. Meanwhile, virtually none of the study's healthy subjects showed any trace of it in their bloodstream.

The chance the virus was there by accident in chronic fatigue sufferers was "infinitesimally small," lead study author Judy Mikovits told the Star at the time.

"(The virus) undoubtedly causes some of the symptoms that are associated with it (chronic fatigue)," said Mikovits, research director of Nevada's Whittemore Peterson Institute for Neuro-immune Diseases.

Mikovits said the virus had almost certainly entered the U.S. blood supply system, but did not know whether it would be susceptible to the same heat treatments that successfully kill off the AIDS virus in blood products.

Three subsequent studies, however, have cast strong doubt on Mikovits' findings. Those papers, all released this year, showed little or no link between the virus and chronic fatigue, also known as myalgic encephalitis.

Last September, researchers from the University of Utah also found the virus in prostate cancer cells. While XMRV was shown to be present, researchers found no evidence it contributed to the disease's onset.

Cancer patients are already prohibited from donating blood in Canada, Devine says.

She says her service is part of an international effort to create an effective screening tool that could look for XMRV in all donated blood, should a definitive link to chronic fatigue be found. Because it resembles HIV, she says, the same heating process that can rid blood products like clotting agents of the AIDS virus should also work to kill XMRV.

An estimated 340,000 Canadians are diagnosed with chronic fatigue. But Devine says most would be too ill to give blood already and there is little chance the current supply has been contaminated.