con·​ta·​gious | \ kən-ˈtā-jəs How to pronounce contagious (audio) \

Definition of contagious

1 : transmissible by direct or indirect contact with an infected person contagious diseases contagious intestinal illness contagious skin rash contagious viruses — see also contagious disease
2 : bearing contagion contagious people
3 : used for contagious diseases a contagious ward
4 : exciting similar emotions or conduct in others contagious enthusiasm contagious laughter

Other Words from contagious

contagiously adverb
contagiousness noun

What is the Difference Between contagious and infectious?

The words contagious and infectious can be confusing because they do not designate wholly distinct categories; something is not either contagious or infectious.

Essentially, infectious diseases and contagious diseases are caused by disease-producing agents such as bacteria and viruses, but they differ in that contagious diseases can be spread to other people by direct or indirect contact.

Anything contagious, such as the flu, is always automatically infectious: if you can catch it from someone, it's being passed to you via an infectious agent, which is the thing that gets you sick—usually a virus or a bacteria.

The reverse, however, isn't true. Just because something is infectious does not mean it's contagious. Food poisoning, for example, is infectious but not contagious: food can be contaminated with a bacteria (an infectious agent) that makes you sick, but you can't give your food poisoning to someone else by shaking their hand or even giving them a kiss.

Both contagious and infectious are also used figuratively, often in much happier contexts: laughter can be contagious; someone's enthusiasm can be infectious. While both words are used figuratively of both pleasant and unpleasant things, contagious is more often chosen for the unpleasant, as when it's grumpiness or fear that seems to be spreading.

Examples of contagious in a Sentence

It's a highly contagious virus. I have a cold and I'm still contagious. I'm sick, but the doctor says I'm not contagious.
Recent Examples on the Web Gilbert has also noted that outbreaks of the extremely contagious peste des petits ruminants virus have also been recently confirmed in mountainous areas of Nepal. Ben Ayers, Outside Online, 27 July 2022 Covid cases and hospitalizations are on the rise in the U.S. and around the world as the extremely contagious omicron BA.5 subvariant continues to spread. Madeline Halpert, Forbes, 25 July 2022 However, the clinical trials took place before the emergence of the extremely contagious omicron variant and its subvariants, which have been found to be more skilled at evading some of the immunity provided by other vaccines than previous strains. Berkeley Lovelace Jr., NBC News, 13 July 2022 That was down 1% from a year earlier and means 35,000 U.S. children entered kindergarten without evidence that they were vaccinated for extremely contagious diseases, the federal Centers for Disease Control and Prevention said in a report. Lindsey Tanner, Chicago Tribune, 21 Apr. 2022 But for extremely contagious diseases such as measles — which is more infectious than coronavirus — even the smallest decline in vaccination coverage can compromise herd immunity and lead to outbreaks. Washington Post, 21 Apr. 2022 In China, a spike in cases, attributed to the extremely contagious Omicron variant, has prompted massive shutdowns. Los Angeles Times, 19 Mar. 2022 Omicron is extremely contagious, unvaccinated people pose more risk than vaccinated ones and the best masks reduce but do not eliminate the risk of contagion, especially in a small space like an elevator. New York Times, 15 Feb. 2022 And down the line, there may be a vaccine specifically made to fight this extremely contagious variant of COVID-19. Taylor Wilson, USA TODAY, 26 Jan. 2022 See More

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

First Known Use of contagious

14th century, in the meaning defined at sense 1

History and Etymology for contagious

Middle English, "contaminating, communicable," borrowed from Anglo-French & Late Latin; Anglo-French, borrowed from Late Latin contāgiōsus, from Latin contāgiō "contact, contagion" + -ōsus -ous

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The first known use of contagious was in the 14th century

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Dictionary Entries Near contagious



contagious abortion

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Last Updated

16 Aug 2022

Cite this Entry

“Contagious.” Dictionary, Merriam-Webster, Accessed 16 Aug. 2022.

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More Definitions for contagious


con·​ta·​gious | \ kən-ˈtā-jəs How to pronounce contagious (audio) \

Kids Definition of contagious

1 : able to be passed from one individual to another through contact a contagious disease
2 : having a sickness that can be passed to someone else
3 : causing other people to feel or act a similar way a contagious laugh


con·​ta·​gious | \ -jəs How to pronounce contagious (audio) \

Medical Definition of contagious

1 : communicable by contact tuberculosis in the contagious stage
2 : bearing contagion many persons … are contagious long before they are aware of the presence of their diseaseJournal of the American Medical Association
3 : used for contagious diseases a contagious ward

Other Words from contagious

contagiously adverb
contagiousness noun

More from Merriam-Webster on contagious

Nglish: Translation of contagious for Spanish Speakers

Britannica English: Translation of contagious for Arabic Speakers


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