virus

noun
vi·rus | \ ˈvī-rəs \
plural viruses

Definition of virus 

1a : any of a large group of submicroscopic infective agents that are usually regarded as nonliving extremely complex molecules, that typically contain a protein coat surrounding an RNA or DNA core of genetic material but no semipermeable membrane, that are capable of growth and multiplication only in living cells, and that cause various important diseases in humans, animals, and plants also : filterable virus

b : a disease or illness caused by a virus

c : the causative agent of an infectious disease

2 : something that poisons the mind or soul the force of this virus of prejudice —V. S. Waters

3 : a computer program that is usually disguised as an innocuous program or file, that often produces copies of itself and inserts them into other programs, and that when run usually performs a malicious action (such as destroying data or damaging software)

4 archaic : venom sense 1

Examples of virus in a Sentence

Is the illness caused by bacteria or a virus? I think I have the virus that's going around this winter. The software checks your hard drive for viruses.
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Recent Examples on the Web

Once a cell has become infected by a virus, the interferons alert the surrounding cells. Lucy Cooke, ajc, "US military is interested in bats as possible defenders against bioweapons," 3 July 2018 Flu is a contagious respiratory illness, spread by a virus. Mike Stobbe, chicagotribune.com, "Flu season was one of the deadliest in recent history for U.S. children," 8 June 2018 Flu is a contagious respiratory illness, spread by a virus. CBS News, "This flu season was the deadliest for U.S. kids in almost a decade," 8 June 2018 Flu is a contagious respiratory illness, spread by a virus. Mike Stobbe, BostonGlobe.com, "Flu season was one of the deadliest for US children," 8 June 2018 The patients, treated last year at different hospitals, had adult T-cell leukemia-lymphoma, which is caused by a virus. Denise Grady, New York Times, "A Promising Cancer Treatment Made Patients Worse, Not Better," 5 June 2018 The disease of the liver, caused by a virus, can be spread person-to-person or through contaminated food or water. Darcy Costello, The Courier-Journal, "Louisville hepatitis A outbreak FAQs: Where can you get a vaccine? How long do shots last?," 20 Apr. 2018 According to Marwa Eltagouri of the Washington Post, the Youngstown raccoons’ odd behavior can likely be ascribed to brain damage caused by the virus. Brigit Katz, Smithsonian, "‘Zombie-Like’ Raccoons Are Terrorizing Youngstown, Ohio," 6 Apr. 2018 Measles is a respiratory disease caused by a virus. Lynn Horsley, kansascity, "Three measles cases confirmed in Johnson County," 13 Mar. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'virus.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of virus

1599, in the meaning defined at sense 4

History and Etymology for virus

Latin, venom, poisonous emanation; akin to Greek ios poison, Sanskrit viṣa; in senses 1 & 3, from New Latin, from Latin

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Statistics for virus

Last Updated

31 Aug 2018

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Time Traveler for virus

The first known use of virus was in 1599

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More Definitions for virus

virus

noun
vi·rus | \ ˈvī-rəs \

Kids Definition of virus

1 : a disease-causing agent that is too tiny to be seen by the ordinary microscope, that may be a living organism or may be a very special kind of protein molecule, and that can only multiply when inside the cell of an organism

2 : a disease caused by a virus

3 : a usually hidden computer program that causes harm by making copies of itself and inserting them into other programs

virus

noun
vi·rus | \ ˈvī-rəs \

Medical Definition of virus 

1a : the causative agent of an infectious disease

b : any of a large group of submicroscopic, infective agents that are usually regarded as nonliving, extremely complex molecules or sometimes as very simple microorganisms, that typically contain a protein coat surrounding an RNA or DNA core of genetic material but no semipermeable membrane, that are capable of growth and multiplication only in living cells, and that cause various important diseases in humans, animals, and plants also : filterable virus

c : a disease caused by a virus

2 : an antigenic but not infective material (as vaccine lymph) obtainable from a case of an infectious disease

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