The prevailing hypothesis is that multiple forces combine to cause colony collapse disorder, such as pesticide exposure, parasites and possibly IAPV, Cox-Foster reported.
Viruses belonging to the group including IAPV linger in pollen.
He points out that IAPV has turned up in colonies that don't collapse, as if they're usually healthy enough to cope with it.
But it also neither rules out nor reinforces the association between IAPV and CCD; it just settles the question of whether the recently imported Australian bees were the original source.
The historical presence of IAPV in the United States does lead to a new question: Are there differences in virulence between imported and domestic IAPV strains?
They now know that the presence of IAPV is a strong sign that a colony has the disorder.
Scientists are still trying to figure out how IAPV came to the United States.
Researchers haven't yet tested whether IAPV meets the standard requirements, called Koch's postulates, that would define it as the cause of colony-collapse disorder.
Whether IAPV contributes to colony collapse or just shows up as a consistent indicator, "both would be good news; says bee geneticist Gene Robinson of the University of Illinois at Urbana-Champaign.
She and her colleagues have found IAPV in live bees from two suppliers in Australia and in packages of royal jelly, bee food for larvae destined to be queens, exported from China.