Cells that support viral replication are called permissive. Infections of permissive cells are usually productive because infectious progeny virus is produced. Most productive infections are called cytocidal (cytolytic) because they kill the host cell. Infections of nonpermissive cells yield no infectious progeny virus and are called abortive. When the complete repertoire of virus genes necessary for virus replication is not transcribed and translated into functional products the infection is referred to as restrictive. In persistent and in some transforming infections, viral nucleic acid may remain in specific host cells indefinitely; progeny virus may or may not be produced.
