- an ultramicroscopic (20 to 300 nm in diameter), metabolically inert, infectious agent that replicates only within the cells of living hosts, mainly bacteria, plants, and animals: composed of an RNA or DNA core, a protein coat, and, in more complex types, a surrounding envelope.
- Informal. a viral disease.
- a corrupting influence on morals or the intellect; poison.
- a segment of self-replicating code planted illegally in a computer program, often to damage or shut down a system or network.
Origin of virus
Examples from the Web for viruses
Plus there is another problem that the viruses pose—the problem that apparently is the culprit this year—they evolve.When You Get the Flu This Winter, You Can Blame Anti-Vaxxers
January 1, 2015
On the one hand, patients may not understand that viruses are the cause of most cold symptoms this time of year.Without Education, Antibiotic Resistance Will Be Our Greatest Health Crisis
December 19, 2014
What specific bacteria and viruses can be detected in the sewage?The Secret to Tracking Ebola, MERS, and Flu? Sewers
November 29, 2014
Scientists increasingly began hunting for viruses in bats—and finding them.
Humans are exposed to viruses from other species all the time, and we almost never get sick.
"I read your thematic on Venusian viruses," he said abruptly.Competition
I kept thinking of viruses—should have seen the obvious sooner.Space Prison
Formerly it was believed that these viruses were morbid entities.Louis Pasteur
And you know, of course, that viruses also have this self-duplicating ability.Category Phoenix
There were viruses, too, and he had been afraid when he had discovered this fact that he had arrived too late.The Invader
- any of a group of submicroscopic entities consisting of a single nucleic acid chain surrounded by a protein coat and capable of replication only within the cells of living organisms: many are pathogenic
- informal a disease caused by a virus
- any corrupting or infecting influence
- computing an unauthorized program that inserts itself into a computer system and then propagates itself to other computers via networks or disks; when activated it interferes with the operation of the computer
Word Origin and History for viruses
late 14c., "venomous substance," from Latin virus "poison, sap of plants, slimy liquid," probably from PIE root *weis- "to melt away, to flow," used of foul or malodorous fluids, with specialization in some languages to "poisonous fluid" (cf. Sanskrit visam "poison," visah "poisonous;" Avestan vish- "poison;" Latin viscum "sticky substance, birdlime;" Greek ios "poison," ixos "mistletoe, birdlime; Old Church Slavonic višnja "cherry;" Old Irish fi "poison;" Welsh gwy "fluid, water," gwyar "blood"). Main modern meaning "agent that causes infectious disease" first recorded 1728. The computer sense is from 1972.
- Any of a large group of submicroscopic agents that act as parasites and consist of a segment of DNA or RNA surrounded by a coat of protein. Because viruses are unable to replicate without a host cell, they are not considered living organisms in conventional taxonomic systems. Nonetheless, they are described as live when they are capable of replicating and causing disease.
- A disease caused by a virus.
- Any of various extremely small, often disease-causing agents consisting of a particle (the virion), containing a segment of RNA or DNA within a protein coat known as a capsid. Viruses are not technically considered living organisms because they are devoid of biological processes (such as metabolism and respiration) and cannot reproduce on their own but require a living cell (of a plant, animal, or bacterium) to make more viruses. Viruses reproduce first either by injecting their genetic material into the host cell or by fully entering the cell and shedding their protein coat. The genetic material may then be incorporated into the cell's own genome or remain in the cytoplasm. Eventually the viral genes instruct the cell to produce new viruses, which often cause the cell to die upon their exit. Rather than being primordial forms of life, viruses probably evolved from rogue pieces of cellular nucleic acids. The common cold, influenza, chickenpox, smallpox, measles, mumps, yellow fever, hemorrhagic fevers, and some cancers are among the diseases caused by viruses.
- Computer Science A computer program that duplicates itself in a manner that is harmful to normal computer use. Most viruses work by attaching themselves to another program. The amount of damage varies; viruses may erase all data or do nothing but reproduce themselves.
See computer virus.