virus

American  

[vahy-ruhs] / ˈvaɪ rəs /

noun

plural

viruses

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.

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virus British  

/ 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

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virus Scientific  

/ 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.

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virus ¹ Cultural  

1. See computer virus.

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virus ² Cultural  

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.”)

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virus ³ Cultural  

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.”)

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Usage

What is a virus? A virus is an ultramicroscopic agent that can only reproduce in living cells and is spread through infection. Many viruses cause diseases as part of their reproduction process.Viruses are only 20 to 300 nanometers—so small that even microscopes can’t see them. Viruses are also very simple. They consist of a core made of DNA or RNA, a protein coat that surrounds the core, and sometimes an envelope that surrounds the core.A virus can’t reproduce on its own. Instead, it will infect a living cell and force it to make more copies of the virus. When the virus does this, it stops the cell from whatever it was doing before and, eventually, kills the cell.Viruses are infectious, meaning they often cause symptoms that allow fluids with copies of the virus to spread to other organisms. For example, if you have the flu and cough on another person, your virus-containing saliva and mucus will enter the other person’s body and allow the virus to infect their cells.Because viruses remain inside living cells, it is often impossible to kill the virus without also killing the cell. Usually, your immune system is the only thing that can safely fight a virus.

Discover More

Viruses cause many diseases. (See viral infection.)

Other Word Forms

• antivirus adjective
• virus-like adjective
• viruslike adjective

Etymology

Origin of virus

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”

Example Sentences

Since the hepatitis B vaccine was universally recommended at birth in the early 1990s, the number of newborns infected with the virus each year has fallen to about 20 from 20,000.

From The Wall Street Journal

How efficiently viruses move between cells plays a major role in how dangerous an infection becomes.

From Science Daily

The Health and Human Services Department endorsed on Monday the use of self-administered tests for the virus that causes cervical cancer, to increase access to screening.

From The Wall Street Journal

Last week there were 2,676 people in hospital with the virus – down from just over 3,000 the week before.

From BBC

For most of human history, viruses have been our unseen enemies—particles of RNA and DNA that hijack our cells.

From The Wall Street Journal

Related Words

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