contagious

adjective

con·ta·gious | \ kən-ˈtā-jəs

Definition of contagious

1 : transmissible by direct or indirect contact with an infected person contagious diseases

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 Synonyms & Antonyms What is the Difference Between contagious and infectious? More Example Sentences Learn More about contagious

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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

Measles is a highly contagious disease caused by a virus that can spread through the air when an infected person coughs or sneezes or if someone comes into direct contact or shares germs by touching the same objects or surfaces. — Cheri Mossburg And Hollie Silverman, CNN, "A UCLA employee infected with measles ate at a campus food court while contagious," 10 July 2019 Hepatitis A is a contagious disease that causes inflammation of the liver. — Claire Rafford, azcentral, "First death in Maricopa County recorded from Hepatitis A outbreak," 9 July 2019 Most carriers say travelers with contagious diseases that could be spread to other passengers can be refused; health officials have recently warned people believed to be infected with measles that they could be prevented from getting on a plane. — The Washington Post, The Mercury News, "Can airlines force travelers off a plane for being sick?," 29 June 2019 Measles is considered one of the most contagious diseases in existence. — Adam Rogers, WIRED, "Fear, Misinformation, and Measles Spread in Brooklyn," 24 June 2019 From Los Angeles to Kentucky, across the USA, experts said, growing homeless populations are increasingly susceptible to outbreaks of contagious diseases, including typhus, Hepatitis A and Shigella. — Chris Woodyard, USA TODAY, "As homeless are suffering, risk of hepatitis, typhus and other diseases is growing," 18 June 2019 The building has only one entrance, which means that anyone who entered or exited the library within two hours of that person’s visit potentially was exposed to one of the most contagious diseases on Earth. — Kaiser Health News, oregonlive.com, "Measles outbreaks require meticulous detective work to halt the spread," 15 June 2019 Hepatitis A is a contagious liver disease that results from exposure to the Hepatitis A virus, including from food, according to the FDA. — The Enquirer, Cincinnati.com, "Kroger recalls 'Private Selection' frozen berries for possible Hepatitis A contamination," 9 June 2019 Hepatitis A is a contagious liver disease that results from exposure to the Hepatitis A virus, including from food, the FDA said. — Casey Smith, Indianapolis Star, "Kroger recalls select frozen berries citing possible Hepatitis A contamination," 8 June 2019

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.

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More Definitions for contagious

contagious

adjective

English Language Learners Definition of contagious

: able to be passed from one person or animal to another by touching

: having a sickness that can be passed to someone else by touching

: capable of being easily spread to others : causing other people to feel or act a similar way

See the full definition for contagious in the English Language Learners Dictionary

contagious

adjective

con·ta·gious | \ kən-ˈtā-jəs

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

contagious

adjective

con·ta·gious | \ -jəs

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 disease — Journal of the American Medical Association

3 : used for contagious diseases a contagious ward