Virus particle, computer illustration. Virus particles (virions) consist of an outer protein coat (capsid) encasing either RNA (ribonucleic acid) or DNA (deoxyribonucleic acid), the genetic material of the virus. Viruses infect their host's cells and duplicate within them. They then exit the host cell (thereby killing it) and go on to infect and kill other cells. Though they exhibit life-like behaviour, viruses are not living organisms.