virus

[ vahy-ruhs ]

noun

, plural vi·rus·es.

1. an ultramicroscopic (20 to 300 nanometers 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.
2. a viral disease:

   He stayed home sick with a virus for nearly two weeks.

3. a corrupting influence on morals or the intellect; poison.
4. a segment of self-replicating code planted illegally in a computer program, often to damage or shut down a system or network.

virus

/ ˈvaɪrəs /

noun

1. 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
2. informal.
   a disease caused by a virus
3. any corrupting or infecting influence
4. 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

virus

/ vī′rəs /

, Plural viruses

1. 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.
2. 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.

virus

¹

1. plur. viruses Microorganisms consisting of DNA and RNA molecules wrapped in a protective coating of proteins . Viruses are the most primitive form of life. They depend on other living cells for their reproduction and growth. ( See under “Medicine and Health.” )

virus

²

1. plur. viruses A minute organism that consists of a core of nucleic acid surrounded by protein . Viruses, which are so small that a special kind of microscope is needed to view them, can grow and reproduce only inside living cells . ( See under “Life Sciences.” )

virus

³

1. See computer virus .

Notes

Viruses cause many diseases. ( See viral infection .)

Derived Forms

• ˈvirus-ˌlike, adjective

Other Words From

• vi·rus·like adjective
• an·ti·vi·rus adjective

Word History and Origins

Origin of virus¹

First recorded in 1590–1600; from Latin vīrus “slime, poison”; akin to Sanskrit viṣá-, Avestan viša-, Greek iós (from earlier wiós, from still earlier wisós ), all meaning “poison, venom”

Word History and Origins

Origin of virus¹

C16: from Latin: slime, poisonous liquid; related to Old English wāse marsh, Greek ios poison

Example Sentences

Authorities believe the virus was acquired via an animal source; however, the teen was not on a farm nor near any known wild birds or backyard poultry — common reservoirs for the disease.

From Los Angeles Times

Dairy industry experts say the virus entered California after local cows were shipped to another state and then returned to California.

From Los Angeles Times

“The idea that we have a child, a teenager, who is seriously ill from this virus is just really an utter tragedy. But sadly, it’s not surprising, given everything we’ve known about H5N1 and its potential to cause illness.”

From Los Angeles Times

Nevertheless, Nuzzo said, while this virus could “be a lot less deadly than what we’ve seen to date,” it could still be far more deadly than any pandemic we’ve seen in a long time, including COVID.

From Los Angeles Times

She said the virus may in the end not end up becoming more virulent or efficient at moving between people, “but I don’t think we want to wait around and on the chance that it might.”

From Los Angeles Times

Related Words

• ailment
• disease
• germ
• illness
• infection
• microbe
• microorganism
• pathogen
• sickness