what is a virus

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A virus is a microscopic particle (ranging in size from 20 - 300 nm) that can infect the cells of a biological organism. Viruses can replicate themselves only by infecting a host cell. They therefore cannot reproduce on their own. At the most basic level, viruses consist of genetic material contained within a protective protein coat called a capsid. They infect a wide variety of organisms: both eukaryotes (animals, yeasts, fungi, and plants) and prokaryotes (bacteria and archaea). A virus that infects bacteria is known as a bacteriophage, often shortened to phage. The word virus comes from the Latin, virus, "poison" (syn. venenum).[1] The study of viruses is known as virology. Those who study viruses are known as virologists