virus

Also known as infectious agent

A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 16,000 of the millions of virus species have been described in detail. The study of viruses is

AI overview

A virus is a tiny infectious agent that can only reproduce by entering living cells and taking over their machinery to make copies of itself. Viruses matter because they infect virtually all life on Earth—from humans and animals to plants and bacteria—making them one of the most important biological forces to understand for human health and ecology.

AI-generated from the Wikipedia summary — may contain errors.

Species

Rose rosette disease

Kingdom

Habitatmarine, brackish, freshwater

Observations3,876

A virus is a small infectious agent that can replicate only inside the living cells of an organism. Viruses can infect all types of organisms, from animals and plants to bacteria and archaea (Koonin et al. 2006). Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants, and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, about 5,000 viruses have been described in detail(Dimmock et al. 2006), although there are millions of different types (Breitbart & Rohwer 2005). Viruses are found in almost every ecosystem on Earth and are the most abundant type of biological entity (Edwards & Rohwer 2005, Lawrence et al. 2009). The study of viruses is known as virology, a sub-speciality of microbiology. Virus particles (known as virions) consist of two or three parts: the genetic material made from either DNA or RNA, long molecules that carry genetic information; a protein coat that protects these genes; and in some cases an envelope of lipids that surrounds the protein coat when they are outside a cell. The shapes of viruses range from simple helical and icosahedral forms to more complex structures. The average virus is

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Research

1,612,665 papers

A Literature Review of Zika Virus.ReviewEmerging infectious diseases · 2016Plourde AR, Bloch EMDOI: 10.3201/eid2207.151990
Nipah virus: pathogenesis, genome, diagnosis, and treatment.ReviewApplied microbiology and biotechnology · 2025Madhukalya R, Yadav U, Parray HA et al.DOI: 10.1007/s00253-025-13474-6
Mutation and Epistasis in Influenza Virus Evolution.ReviewViruses · 2018Lyons DM, Lauring ASDOI: 10.3390/v10080407
Dengue virus: structure, genome, evolution and challenges to control and prevent transmission.ReviewAntonie van Leeuwenhoek · 2025Umar K, Sutradhar T, Prakash P et al.DOI: 10.1007/s10482-025-02153-1
Virus-erythrocyte interactions.ReviewAdvances in virus research · 1972Howe C, Lee LTDOI: 10.1016/s0065-3527(08)60746-0
Advancements in Research on Duck Tembusu Virus Infections.ReviewViruses · 2024Cheng Y, Wang R, Wu Q et al.DOI: 10.3390/v16050811
Zika Virus: A Critical Analysis and Pharmaceutical Perspectives.ReviewCritical reviews in eukaryotic gene expression · 2018Sultan N, Bukhari SA, Ali I et al.DOI: 10.1615/CritRevEukaryotGeneExpr.2018025061
Charting the Proteins of Oropouche Virus.ReviewViruses · 2025Thomas SDOI: 10.3390/v17111434

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Wikidata facts

Image: SARS-CoV-2 without background.png

Show 5 more facts

Commons category: Viruses
taxon name: Virus
Commons gallery: Virus
NCI Thesaurus ID: C14283
hashtag: virus

Sources (5)

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~69 min read

Article

43 sections

Contents

Etymology
Origins
Microbiology
Discovery
Life properties
Structure
Giant viruses
Genome
Genome size
Genetic mutation and recombination
Replication cycle
Genome replication
Cytopathic effects on the host cell
Dormant and latent infections
Host range
Novel viruses
Classification
ICTV classification
Baltimore classification
Role in human disease
Epidemiology
Epidemics and pandemics
Cancer
Host defence mechanisms
Prevention and treatment
Vaccines
Antiviral drugs
Infection in other species
Animal viruses
Plant viruses
Bacterial viruses
Archaeal viruses
Role in aquatic ecosystems
Role in evolution
Applications
Life sciences and medicine
Virotherapy
Materials science and nanotechnology
Synthetic viruses
Weapons
See also
References
External links

When infected, a host cell is often forced to rapidly produce thousands of copies of the original virus. When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent viral particles, or virions, consisting of (i) genetic material, i.e., long molecules of DNA or RNA that encode the structure of the proteins by which the virus acts; (ii) a protein coat, the capsid, which surrounds and protects the genetic material; and in some cases (iii) an outside envelope of lipids. The shapes of these virus particles range from simple helical and icosahedral forms to more complex structures. Most virus species have virions too small to be seen with an optical microscope and are one-hundredth the size of most bacteria.