virus

vi·rus

noun \ˈvī-rəs\

plural vi·rus·es

Definition of VIRUS

1

archaic : venom 1

2

a : the causative agent of an infectious disease

b : any of a large group of submicroscopic infective agents that are regarded either as extremely simple microorganisms or as 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, lower animals, or plants; also : filterable virus

c : a disease or illness caused by a virus

3

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

4

: a computer program that is usually hidden within another seemingly innocuous program and that produces copies of itself and inserts them into other programs and usually performs a malicious action (as destroying data)

Examples of VIRUS

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

Origin of VIRUS

Latin, venom, poisonous emanation; akin to Greek ios poison, Sanskrit viṣa; in senses 2 & 4, from New Latin, from Latin

First Known Use: 1599

Other Microbiology Terms

pathogen, salmonella, tetanus

Rhymes with VIRUS

Cyrus, gyrus, iris, Iris, Skyros

vi·rus

noun \ˈvī-rəs\   (Medical Dictionary)

Medical Definition of VIRUS

1

a : the causative agent of an infectious disease b : any of a large group of submicroscopic infective agents that are regarded either as extremely simple microorganisms or as 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, or 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

virus

noun    (Concise Encyclopedia)

The influenza virus possesses both a protein shell (capsid) and a lipid and protein envelope. The …—© Merriam-Webster Inc.

Microscopic, simple infectious agent that can multiply only in living cells of animals, plants, or bacteria. Viruses are much smaller than bacteria and consist of a single- or double-stranded nucleic acid (DNA or RNA) surrounded by a protein shell called a capsid; some viruses also have an outer envelope composed of lipids and proteins. They vary in shape. The two main classes are RNA viruses (see retrovirus) and DNA viruses. Outside of a living cell, a virus is an inactive particle, but within an appropriate host cell it becomes active, capable of taking over the cell's metabolic machinery for the production of new virus particles (virions). Some animal viruses produce latent infections, in which the virus persists in a quiet state, becoming periodically active in acute episodes, as in the case of the herpes simplex virus. An animal can respond to a viral infection in various ways, including fever, secretion of interferon, and attack by the immune system. Many human diseases, including influenza, the common cold, and AIDS, as well as many economically important plant and animal diseases, are caused by viruses. Successful vaccines have been developed to combat such viral diseases as measles, mumps, poliomyelitis, smallpox, and rubella. Drug therapy is generally not useful in controlling established viral infections, since drugs that inhibit viral development also inhibit the functions of the host cell. See also adenovirus; arbovirus; bacteriophage; picornavirus; plant virus; poxvirus.