Scientists have discovered that 22 species of passerines -- songbirds and perching birds -- in the contiguous U.S. are carriers of low-pathogenicity avian influenza. Pathogenicity is the ability of a germ to produce an infectious disease in an organism. The prevalence of influenza in waterfowl has long been known. But the researchers' analysis indicates that the number of songbird species with low-pathogenicity avian influenza is greater than the number in eight other avian orders, including waterfowl.