Once the virus has infected the cell, it will sooner or later start replicating itself, using the "infrastructure" of the infected cell. During this process, the capsid subunits are synthesized according to the genetic material of the virus, using the Protein biosynthesis mechanism of the cell. Some viruses will also take a portion of the host cell's Cell membrane with them when they depart, enclosing the proteinaceous capsid with viral proteins projecting through it.
The majority of viruses come in three different structures; helical capsids, icosahedral (isometric) capsids, or enveloped. In helical symmetry, the protein subunits are arranged around the Circumference of a circle to form a disk. In icosahedral symmetry, the subunits form a quasi-spherical structure. In enveloped viruses, the protein subunits are exposed to the external environment.