virus /vī″rəs/ [L, poison] , 1. a minute parasitic microorganism much smaller than a bacterium that, having no independent metabolic activity, may replicate only within a cell of a living plant or animal host. A virus consists of a core of nucleic acid (deoxyribonucleic acid or ribonucleic acid) surrounded by a coat of antigenic protein, sometimes surrounded by an envelope of lipoprotein. The virus provides the genetic code for replication, and the host cell provides the necessary energy and raw materials. More than 200 viruses have been identified as capable of causing disease in humans. Kinds include adenovirus, Arenavirus, Enterovirus, herpesvirus, rhinovirus. See also viral infection. 2. (in computer technology) a type of malicious computer code that is designed to spread from computer to computer, or from computer system to computer system, for the purpose of interfering with normal operations.
