infectious

play

adjective in·fec·tious \in-ˈfek-shəs\

Definition of infectious

1a : capable of causing infection viruses and other infectious agentsb : communicable by infection an infectious disease — compare contagious
2 : that corrupts or contaminates
3 : spreading or capable of spreading rapidly to others their enthusiasm was infectious an infectious grin

infectiously

adverb

infectiousness

noun

See infectious defined for English-language learners

See infectious defined for kids

Examples of infectious in a Sentence

viruses and other infectious agents
She has an infectious grin.

Recent Examples of infectious from the Web

The method will speed up immune matching for organ transplant and other purposes such as treating infectious and autoimmune diseases, the scientists say.

— bradley j. fikes, sandiegouniontribune.com, "Immune-matching process improved, reports Human Longevity-led study," 9 July 2017
Jett said the Herpes B virus is incredibly infectious.

— prescotte stokes iii, AL.com, "Monkeys held captive by former zoo employee tested positive for herpes: court documents," 7 July 2017
If a tick is crawling on the skin or is quickly removed, the chance of transmission of any infectious disease is extremely unlikely.

— dennis pillion, AL.com, "Tick-borne illnesses, including Lyme disease, on the rise in Alabama," 3 July 2017
The idea behind an emergency fund is not to displace efforts to combat infectious disease but to ramp them up to meet a crushing temporary need.

— the editors, Scientific American, "Robust Emergency Fund Needed to Respond to Future Disease Outbreaks," 26 June 2017
In North Korea, the focus is on infectious disease and physical trauma, often caused by coal-mining injuries.

— michelle w., Longreads, "Reunification Will Have to Bridge the DMZ and Massive Technological Gaps," 23 June 2017
Dr. Fred Silverblatt, the infectious-disease doctor Jenckes consulted, didn’t think the subtle findings could be the cause of her symptoms.

— lisa sanders, m.d., New York Times, "How a Joke About Flying Squirrels Led to an Ailing Woman’s Cure," 22 June 2017
Among infectious diseases, flu is considered one of the U.S.’s leading killers.

— mike stobbe, The Seattle Times, "Flu vaccine ineffective for people 65 and older last winter," 21 June 2017
Fighting emerging infectious diseases costs billions of dollars, as the AIDS pandemic and the recent Ebola epidemic in West Africa attest.

— betsy mckay, WSJ, "Predicting the Next Pandemic," 21 June 2017

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

First Known Use of infectious

1534

Other Medicine Terms

analgesia, angina, diabetes, hepatitis, homeopathy, logorrhea, palliate, pandemic

INFECTIOUS Defined for English Language Learners

infectious

play

adjective

Definition of infectious for English Language Learners

: capable of causing infection
: capable of being passed to someone else by germs that enter the body
: suffering from a disease that can be spread to other people by germs

INFECTIOUS Defined for Kids

infectious

play

adjective in·fec·tious \in-ˈfek-shəs\

Definition of infectious for Students

1 : passing from one to another in the form of a germ an infectious illness
2 : easily spread to others an infectious laugh

Medical Dictionary

infectious

play

adjective in·fec·tious \in-ˈfek-shəs\

Medical Definition of infectious

1: capable of causing infection a carrier remains infectious without exhibiting signs of disease viruses and other infectious agents
2: communicable by invasion of the body of a susceptible organism all contagious diseases are also infectious, but it does not follow that all infectious diseases are contagious—W. A. Hagan—compare contagious 1