CALGARY — The mysterious Colony Collapse Disorder that's savaging honeybee colonies across the United States and is expected to enter Canada is likely related to a virus, a group of top bee scientists said Thursday.

According to a new report in the journal Science, the Israeli Acute Paralysis Virus (IAPV) may be a potential cause of the epidemic that has afflicted between 50 and 90 per cent of commercial bee colonies in the U.S.

"In this study, we've had opportunity to find a brand-new virus to the United States, and it appears to be associated with (Colony Collapse Disorder),'' Diana Cox-Foster, an entomology professor at Penn State, said on a conference call.

"Whether it's a causative agent or a very good marker is the next major question that we need to address.''

Only recognized last year, the mysterious disorder is different from other diseases that plague bees because nearly all adults disappear from the hive _ leaving only the queen, a few newly hatched insects and plenty of food behind.

Disappearing bees have been reported in 27 states so far and damaged nearly one-quarter of all beekeeping operations in the U.S. last winter.

And the disorder has broader implications for the entire food chain. About one-third of the human diet comes from insect-pollinated plants, with the honeybee performing the great majority of that work.

"The plight of honeybees in this case has raised awareness around the globe to the value of all pollinators,'' said co-author Jeffrey Pettis, the U.S. Department of Agriculture's top bee researcher.

Canadian experts don't believe that Colony Collapse Disorder has crossed the border yet, though health issues and pesticide-resistant mites remain a top concern. Nearly 30 per cent of Canada's bee colonies were killed off last winter -- twice the normal rate.

"Beekeepers have been trying to rebuild over the summer,'' Heather Clay, national co-ordinator for the Canadian Honey Council, said in an e-mail from Melbourne, Australia, where she is attending an international beekeeping conference.

"Although it is too early to tell, it is expected that the honey crop in many areas may be impacted by the lower number of producing colonies.''

Together with infectious disease researchers, the U.S. bee scientists sequenced the genetic material in both healthy and afflicted bees from around the world.

They discovered that while all bees carry a large number of viruses, only one _ the IAPV that was first identified by researchers at Hebrew University in 2004 _ was found in bees that had Colony Collapse Disorder.

IAPV was also found in apparently healthy bees from Australia, which could be a significant clue to the origin of the virus in North America since the U.S. began importing bees from Australia in 2004.

But while IAPV appears linked to the honeybee disorder, researchers say the discovery simply points to the direction of further studies.

"I think we have new leads _ IAPV is one of those leads that must be followed before we can assign true cause and effect with CCD,'' said Pettis.

He believes that other stressors to bee colonies are likely playing a role, including poor nutrition, pesticide exposure and parasitic mites.

"As scientists it's very easy for us to manipulate a single variable, but what we need to do is look at combinations of things.''

Regulations that restrict the importation of U.S. bee colonies may explain why the disorder hasn't yet reached Canada.

But that probably won't last, said Rob Currie, an entomology professor at the University of Manitoba and past-president of the Canadian Association of Professional Apiculturists.

"I think ultimately most pests that end up in the U.S. come across the border, because bees don't respect customs regulations,'' said Currie.

"Many beekeepers transport their colonies all the way from the southern U.S. right up to North Dakota and locate their colonies right along the Canadian border,'' he said.

"And those bees will swarm or fly across and infect bees on the other side.''

The sudden disappearance of so many U.S. honeybees has also led to a variety of myths and theories popping up on the Internet.

The two most popular _ that radiation from cellphones is killing the bees or that genetically modified crops are responsible _ are both "at very low priority,'' said Cox-Foster.

But she said data does suggest that chemical pesticides could be helping to stress the bees or act as a potential trigger of specific viruses.