"The paper is a model of careful investigation," says entomologist Gene Robinson, director of the University of Illinois at Urbana-Champaign's bee research facility, who was not involved in the study. IAPV seems to be either a cause of or a marker for the disease, he says. "Either way, it's the first big breakthrough in the CCD story, so it's very exciting and very encouraging."
The smoking gun, Lipkin says, would be to infect healthy or stressed bees with IAPV and see if they catch CCD. The researchers plan to carry out such tests, but isolating the virus is challenging, he adds.
A broader sampling of diseased and healthy colonies from around the world would also help narrow down what causes the disease, Robinson says.
Lipkin and co-workers found that seemingly healthy Australian bees were infected with the virus and point out that all of the CCD hives they examined included or spent time near imported Australian bees. Beekeepers from Down Under have reported a "disappearing disease" but not on the scale of CCD, Pettis said during a press conference Wednesday.
One difference, he said, could be parasitic varroa mites, which suppress bees' immune systems and have driven down the U.S. bee population by 30 percent in the last 25 years, but are not found in Australia. "We know it's a primary stressor," he added. "I still believe that multiple factors are involved in CCD and we must test [them] in a more rigorous fashion."
The researchers only found varroa mites in half of the diseased U.S. hives. They note, however, that it is possible a mite-killing chemical applied by beekeepers may have killed the parasites off after they did their damage, or the chemical itself could have harmed the bees.
IAPV seems to have first killed bees in Israel in 2002, and since then has caused a varying number of deaths each year, says plant virologist Ilan Sela of The Hebrew University of Jerusalem, whose group identified the virus, which causes dying bees' wings to shiver.
"I was told by the Israeli [beekeeping] extension people that there are some recent indications for a small-scale CCD-like phenomenon in Israel," he says, adding that he has yet to test the afflicted bees for the virus.
If IAPV is causing CCD, there is hope of stopping its spread. About 30 percent of the bees Sela examined have incorporated pieces of the IAPV genome into their chromosomes and are resistant to the virus. Other bees could be bred to carry those fragments and presumably survive infection, too, he says.
But he cautions that IAPV could in theory be causing CCD by inserting its genetic material into bee genes for pheromones or other molecules that coordinate hive behavior, thereby disrupting those genes, a possibility that he and the CCD working group plan to test.
Until researchers have cracked the CCD mystery, Cox-Foster advised beekeepers Wednesday to keep their bees well fed and free of mites.