Scientists have tentatively identified a possible culprit in the mysterious disappearance of honeybees, a phenomenon known as colony collapse disorder. A recently-discovered virus may be the cause, or at least a contributing factor.

Across the United States and elsewhere, bees have been mysteriously disappearing from their hives. It's a worrisome problem for farmers, who depend on honeybees to pollinate many important crops, but anything that affects the food supply obviously concerns anyone who eats.

The 22 co-authors of a paper published online this week in Science Express are careful not to say the virus, known as IAPV, is the cause of colony collapse disorder, or CCD. They don't have enough evidence for that, yet. But there is a relationship between the two, and lead author Diana Cox-Foster says it's a promising clue.

"In this study we've had opportunity to find a relatively new virus to the United States, or a brand new virus to the United States," she told reporters. "It appears to be associated with colony collapse disorder. Whether it's a causative agent or a very good marker is the next major question that we need to address."

Colony collapse disorder has affected more than half the commercial honeybee hives in the United States. The importance of bees as agricultural pollinators has made identifying the source of CCD a top priority for researchers.

In their attempt to identify the cause of the problem, the scientists used genetic sequencing techniques to identify all the microorganisms in the bees.

Edward Holmes of Pennsylvania State University says they discovered a number of viruses, in addition to the one that appears to be linked to CCD. "So we're really left with this remarkable situation now where we know these bees carry this remarkable diversity of viruses. We think one is strongly associated with CCD. But the bigger question is really how these viruses interact in the population. That we really don't know."

In addition to the viruses, Researcher Nancy Moran of the University of Arizona says they found previously unknown bacteria, mainly in the guts, the intestines of bees. They don't appear to have anything to do with CCD, since they were found in both sick and healthy bees. And Moran says the role these bacteria play is unclear.

"In other insects it's known that bacteria can provide essential nutrients that the insect requires for nutrition, or that they can contribute defenses against pathogens or natural enemies," Moran said. "At this point we don't know what these bacteria are doing in bees, but we know they're present in all bees sampled and they're a very distinctive set."

The suspect virus was first identified by a researcher in Israel, so it's called Israeli Acute Paralysis Virus - IAPV for short. And if IAPV is the cause of colony collapse disorder, or even if it just contributes to it, the research reported this week could provide a blueprint to help combat the puzzling phenomenon.

Jeff Pettis of the U.S. Department of Agriculture says nailing down the cause will be a next step. "I still believe that multiple factors are involved in CCD and we must test those combinations in a more rigorous fashion. As scientists, it's very easy for us to manipulate a single variable, but what we really need to do is begin to look at combinations of things, such as the interactions between varroa [parasitic mites], pesticide stress, and nutrition."

Pettis adds that identifying those other contributing factors may be even more important to solving the problem. In the meantime, those who keep bees should do what they can to keep their hives as healthy as possible by following good beekeeping practices.

"Let's say this virus story was true and it was working in combination with some other factor," Pettis said, "we're not going to likely come up with a treatment for viruses in bees. So we're going to have to manage the other part, the parts that we can manage, and keep the virus levels at low levels so that they're not affecting bee health."

Jeff Pettis stresses that the problem of colony collapse disorder has not yet been solved, and that much more research is needed to completely understand this puzzling and potentially devastating problem.

Incidentally, while the researchers are not completely ruling out other possible causes of colony collapse disorder, they say it appears increasingly unlikely it's due to electromagnetic radiation from mobile phones or the impact of genetically modified crops. Chemical pesticides, however, are still being studied as a possibly contributing cause.