title: [What is a virus?].
abstract: Viruses are simple biological particles, consisting of a genome, a protein capsid and, in the case of enveloped viruses, an external lipidic envelope. Owing to the presence of envelope, most enveloped viruses are fragile although some exceptions may be observed. Viruses behave as complete intracellular parasites. Their multiplication results from the replication and self-assembly of viral components, this process being directed by the viral genome after it has been released within an infected cell. Virus classification is now essentially based on molecular properties, concerning both the structure and replication strategy of viruses. In virus taxonomy, serial hierarchical levels are family, subfamily, genus and species. Within species, lower hierarchical levels are type, subtype, variant and strain. Knowledge of virus structure and classification is essential for considering the physiopathology, diagnosis and therapy of viral infections.
authors.affiliation: Laboratoire de virologie du CERVI, Paris.
authors.forename: H
authors.initials: H
authors.lastname: Agut
authors.forename: A M
authors.initials: AM
authors.lastname: Fillet
authors.forename: V
authors.initials: V
authors.lastname: Calvez
mesh_terms: D006801:Humans; D009626:Terminology as Topic; D014764:Viral Proteins; D014777:Virus Diseases / Q000175:diagnosis* / Q000628:therapy / Q000821:virology; D014779:Virus Replication; D014780:Viruses / Q000145:classification / Q000648:ultrastructure
chemical_list: D014764:Viral Proteins