Virus Taxonomy Online: (Left) Model of Chicken anemia virus (CAV) capsid, for which a class P = 3 icosahedron with a T = 3 has been proposed. The model is viewed down a two-fold axis of symmetry. (Right) Negative contrast electron microscopy of CAV particles stained with uranyl acetate. (Courtesy of M.S. McNulty.) The bar represents 50 nm.