contagious

adjective

con·​ta·​gious kən-ˈtā-jəs How to pronounce contagious (audio)
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
contagiously adverb
contagiousness noun

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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 But like Salmonella typhi, norovirus infections can be contagious without any symptoms at all. Sabrina Sholts, Smithsonian Magazine, 12 Mar. 2024 The new research suggests why: The virus is not always fully cleared after the initial infection, so remains deeply embedded, even though people are no longer contagious. Lisa M. Krieger, The Mercury News, 11 Mar. 2024 People are contagious up to four days before symptoms appear and the rate of complications is high, Bagdasarian said. Kristen Jordan Shamus, Detroit Free Press, 10 Mar. 2024 Most people who have symptoms and test positive are contagious. Anuradha Rao, The Conversation, 1 Mar. 2024 The recent attention to contagious measles, tuberculosis, Ebola, and other illness outbreaks in the news has once more brought to light the threat that pandemics and bioterrorism pose. Chuck Brooks, Forbes, 29 Feb. 2024 In these non-congregate motel shelters, people could socially distance and curb the spread of the highly contagious virus. Ariane Lange, Sacramento Bee, 27 Feb. 2024 The character brings a contagious sense of optimism to an otherwise dry athletic scene and leans into camaraderie over external praise. Kelly Wynne, Peoplemag, 25 Feb. 2024 Measles is a highly contagious respiratory disease that was largely eradicated in the United States by 2000 thanks to vaccines, according to the Centers for Disease Control and Prevention. Binghui Huang, The Indianapolis Star, 23 Feb. 2024

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'contagious.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

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

First Known Use

14th century, in the meaning defined at sense 1

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

Dictionary Entries Near contagious

Cite this Entry

“Contagious.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/contagious. Accessed 18 Mar. 2024.

Kids Definition

contagious

adjective
con·​ta·​gious kən-ˈtā-jəs How to pronounce contagious (audio)
1
a
: able to be passed on by contact between individuals
colds are contagious
contagious diseases
b
: capable of passing on a contagious disease to another
he is contagious
2
: so pleasantly irresistible as to be picked up by one person after another
your enthusiasm is contagious
Etymology

Middle English contagious "likely to be passed on through contact," from early French contagieus (same meaning), derived from Latin contingere "to have contact with, affect, happen" — related to contact, contingent

Medical Definition

contagious

adjective
con·​ta·​gious -jəs How to pronounce contagious (audio)
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
contagiously adverb
contagiousness noun

More from Merriam-Webster on contagious

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