in·​fect | \ in-ˈfekt How to pronounce infect (audio) \
infected; infecting; infects

Definition of infect

transitive verb

1 : to contaminate with a disease-producing substance or agent (such as bacteria)
2a : to communicate a pathogen or a disease to
b of a pathogenic organism : to invade (an individual or organ) usually by penetration
c of a computer virus : to become transmitted and copied to (a device, such as a computer)
3a : contaminate, corrupt the inflated writing that infects such stories
b : to work upon or seize upon so as to induce sympathy, belief, or support trying to infect their salespeople with their enthusiasm

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Other Words from infect

infector \ in-​ˈfek-​tər How to pronounce infect (audio) \ noun

Examples of infect in a Sentence

If you're sick you should stay home to avoid infecting other people in the office. The virus has infected many people. They were unable to prevent bacteria from infecting the wound. Her enthusiasm has infected everyone. The virus has infected many computers. All the computers in the office were infected by the same virus.
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Recent Examples on the Web Transmission also involved two clusters that saw teachers infect one another during in-person meetings or lunches, with the teacher subsequently infecting other students. Dallas News, "Teachers may be more significant in the spread of COVID-19 than students, a new study reveals.," 22 Feb. 2021 For example, Monilinia fungi infect blueberries and huckleberries and transform the plants’ leaves into flowery-smelling, sugar-secreting and ultraviolet-reflecting enticements for pollinating insects, according to the Guardian. Alex Fox, Smithsonian Magazine, "This Fungus Makes Convincing Fake Flowers From Scratch," 19 Feb. 2021 Bazemore’s jobs are to help organize the offense and take advantage of opponents’ focus on Curry, and to effortlessly switch on defense and infect his teammates with energy on that end. Rusty Simmons, San Francisco Chronicle, "Kent Bazemore scores 20 points; provides more leadership after Warriors' loss," 6 Feb. 2021 It’s the spike protein that helps the virus enter cells and infect people. Daniela Hernandez, WSJ, "Why the New Covid-19 Variants Could Be More Infectious," 16 Jan. 2021 The Ducks didn’t want players being around family at all out of fear that a parent infected with coronavirus could pass it along to their son, who then could infect teammates. oregonlive, "Emotions flow for Oregon Ducks parents watching sons play, reconnecting at Fiesta Bowl to end trying season," 3 Jan. 2021 Other mutations might allow variants of SARS-CoV-2 to escape from current vaccines and infect people who were once immune. Ed Yong, The Atlantic, "Pandemic Year Two," 29 Dec. 2020 Local officials say the source of many infections are from home and family gatherings, where younger individuals, who may not have symptoms of the disease, infect older adults. Naseem S. Miller,, "COVID-19 hospitalizations continue to climb in Central Florida," 29 Dec. 2020 The first deaths were reported four days later, and COVID-19 would go on to infiltrate every corner of life for the rest of the year, infect more than 1.2 million Floridians and kill at least 20,700. David Schutz,, "These are the 20 most-read stories of 2020 on," 24 Dec. 2020

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

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First Known Use of infect

14th century, in the meaning defined at sense 2a

History and Etymology for infect

Middle English infecten, enfecten "to inflict with disease, pollute, damage, corrupt," borrowed from Latin infectus, past participle of inficere "to dye, discolor, impregnate, taint, contaminate with disease," from in- in- entry 2 + facere "to make, bring about, perform, do" — more at fact

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Time Traveler for infect Time Traveler

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

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Statistics for infect

Last Updated

28 Feb 2021

Cite this Entry

“Infect.” Dictionary, Merriam-Webster, Accessed 8 Mar. 2021.

Style: MLA
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More Definitions for infect



English Language Learners Definition of infect

: to cause (someone or something) to become sick or affected by disease
: to cause (someone) to feel an emotion
of an emotion : to spread to (other people)


in·​fect | \ in-ˈfekt How to pronounce infect (audio) \
infected; infecting

Kids Definition of infect

1 : to pass on or introduce a germ, illness, or disease to : to cause sickness in Don't infect me with your cold. The bacteria can infect wounds.
2 : to cause to share similar feelings Her enthusiasm infects the other players.
in·​fect | \ in-ˈfekt How to pronounce infect (audio) \

Medical Definition of infect

1 : to contaminate with a disease-producing substance or agent (as bacteria)
2a : to communicate a pathogen or a disease to
b of a pathogenic organism : to invade (an individual or organ) usually by penetration — compare infest

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