Viruses are obligate intracellular parasites. Union of performed components to produce virus particles. Mature virus particles are called VIRIONS. Genetic material is complexed with proteins and packaged into a protein coat called a CAPSID. A suitable host must be grow in culture as viruses can be only studied that way.. PLAQUES are areas of lysis caused by a viral infection. They have a simple replication cycle e.g. single virion attaches to and infects a host cell. Two time scales for this process: lytic viruses and latent period.