Plural of virus

regular plural

The plural of virus is viruses.

Forms of virus

Less standard forms: viri (proscribed), virii (proscribed), virus (nonstandard).

Bats host many high-profile viruses that can infect humans, including severe acute respiratory syndrome and Ebola.2013 May-June, Katie L. Burke, “In the News”, in American Scientist, volume 101, number 3, page 193
Some viruses, such as norovirus, cause sporadic outbreaks of gastroenteritis.
Viruses depend on the host that they infect in order to be able to reproduce.From the entry host
Examples of anthropozoonoses include brucellosis bacteria or rabies and Ebola viruses.From the entry anthropozoonosis
Horse viruses are in Pat’s wheelhouse.From the entry wheelhouse

noun A submicroscopic, non-cellular structure that consists of a core of DNA or RNA surrounded by a protein coat, that requires a living host cell to replicate, and that sometimes causes disease in the host organism (such agents are often classed as nonliving infectious particles and less often as microorganisms).
noun A species thereof.
noun An individual particle thereof: synonym of virion.

What is the plural of virus?: The plural of virus is viruses.
Is virus countable?: Virus is a countable and uncountable noun.
Is viri correct?: viri is marked proscribed in Wiktionary. The usual plural of virus is viruses.
Is virii correct?: virii is marked proscribed in Wiktionary. The usual plural of virus is viruses.

Adapted from Wiktionary: virus (page history and authors) and the entries of its forms. Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws left out forms marked obsolete, archaic, rare or dialectal and added the examples. Wiktionary data of 2026-09-02.

Last updated: 2026-09-02

Cite this page: “Plural of virus.” Word.ws, https://word.ws/plural/virus. Based on Wiktionary, CC BY-SA 4.0.