A viral pathogen that typically infects plants has been found in honeybees and could help explain a decline in their numbers, U.S. researchers say. It could be involved in the phenomenon known as Colony Collapse Disorder, a mysterious malady that has wiped out entire hives in the United States since it was first identified in 2006, a release from the American Society for Microbiology said Tuesday. A routine screening of bees for frequent and rare viruses "resulted in the serendipitous detection of Tobacco Ringspot Virus, or TRSV, and prompted an investigation into whether this plant-infecting virus could also cause systemic infection in the bees," Yan Ping Chen from the U.S. Department of Agriculture's Agricultural Research Service laboratory in Beltsville, Maryland, said. About 5 percent of known plant viruses are pollen-transmitted and thus potential sources of host-jumping viruses that could infect bees, the researchers said. "The increasing prevalence of TRSV in conjunction with other bee viruses is associated with a gradual decline of host populations and supports the view that viral infections have a significant negative impact on colony survival," the researchers said. The team of researchers from the United States and China has reported their findings in the journal mBio.