Nature of viruses

Viruses exist in two different states, the extracellular infectious particle or virion and the intracellular state consisting of viral nucleic acid.

The virion consists of a protein coat or capsid, which encloses a genome of either RNA or DNA. The entire structure is called the nucleocapsid.

The capsid may be a polyhedron or a helix, or a combination of both (in some phages). Viruses are infective micro­organisms that show several differences from typical microbial cells.
They show both animal and plant characteristics so they cannot be classified as any particular group.