Viruses are small infectious agents that are able to replicate only in living cells. They are known for their ability to produce disease in their animal and plant hosts, and they have played a prominent role in the recent expansion of knowledge in the fields of cell and molecular biology.

Keywords: virus; vaccine; infectious agent; virus replication; oncogenic virus; oncogene; gene therapy

Figure 1.

Electron micrograph of herpes simplex virus. Note that the capsid is surrounded by a membrane envelope. Bar, 40 nm.

Figure 2.

Electron micrograph of poliovirus. Note that poliovirus is much smaller than herpes simplex and that it lacks a membrane envelope. Bar, 30 nm.

Figure 3.

Structure of a helical virus, tobacco mosaic virus. A schematic representation of the virus structure (a) and an electron micrograph of the virus (b) are shown.

Figure 4.

Structure of an icosahedral virus capsid, herpes simplex virus. A drawing of an icosahedron (a) and the herpes simplex capsid (b) are shown.

Figure 5.

The genome of human papillomavirus. Positions of the regions coding for the E1E7 and L1L2 genes are indicated.

Figure 6.

Virus attachment to a host cell.

Figure 7.

Accumulation of mature progeny virions inside an infected cell.

Figure 8.

Release of progeny virus by lysis of a host cell.

Figure 9.

Protocol for treatment of a patient by gene therapy. The gene to be introduced into patient cells is cloned into a virus genome (upper right) and packaged into the virus. The virus is then employed to deliver the gene to the patient, where it is expressed in the patient' cells. Presence of the novel protein complements the defect originally present in the patient.


Further Reading

Fields BN, Knipe DM, Howley PM et al. (1996) Fields Virology, 3rd edn. Philadelphia: Lippincott‐Raven.

Flint SJ, Enquist LW, Krug RM, Racaniello VR and Skalka AM (2000) Principles of Virology: Molecular Biology, Pathogenesis and Control. Herndon, VA: ASM Press.

Levine AJ (1992) Viruses. New York: Freeman.

Martelli GP, Mayo MA and Summers MD (eds) (1995) Virus Taxonomy, Classification and Nomenclature of Viruses: Sixth Report of the International Committee on Taxonomy of Viruses. Vienna: Springer.

Sauder DM (2000) All the Virology on the World Wide Web. [∼dmsander/garryfavweb.html]

Wagner EK and Martinez JH (1999) Basic Virology. Malden, MA: Blackwell Science.

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Brown, Jay C(Jul 2003) Virology. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0000435]