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 Both Ghaly and officials in England said the changes make the virus more likely to infect people who are exposed to it. Soumya Karlamangla, Los Angeles Times, "L.A. County is probing whether a new, more contagious COVID strain is spreading locally," 25 Dec. 2020 During the study, scientists would purposely infect up to 100 young, healthy volunteers with the coronavirus that causes Covid-19 in the hopes of accelerating the search for new vaccines. Theresa Machemer, Smithsonian Magazine, "A Brief History of Human Challenge Trials," 16 Dec. 2020 Problems that arise in the commercial affiliate are likely to infect the bank, as shown by the recent collapse of Wirecard in Germany. Fortune, "Why it would be a huge mistake to allow Big Tech firms to acquire banks," 26 Nov. 2020 Antigen: a quick, on-the-spot test that’s less sensitive than PCR but good at identifying people who are most likely to infect others. Lisa Song, ProPublica, "Rapid Testing Is Less Accurate Than the Government Wants to Admit," 16 Nov. 2020 But adjacent parties of diners in separate bubbles are not likely to infect one another, a Brigham and Women’s Hospital doctor who specializes in infectious diseases is quoted as saying. Robin Lloyd, Scientific American, "Coronavirus News Roundup, October 31-November 6," 6 Nov. 2020 Cell Antibodies block a spike protein on the virus’s surface that normally helps the virus latch onto and infect cells. Sarah Toy, WSJ, "Highly Touted Monoclonal Antibody Therapies Sit Unused in Hospitals," 27 Dec. 2020 The method used in the new trial involves using a virus carrying the factor IX gene to infect liver cells. John Timmer, Ars Technica, "A promising start to new human gene-editing trials," 9 Dec. 2020 The species, including dolphins, beluga whales, sea otters and seals, have a specific receptor called ACE2 that allows SARS-CoV-2 to infect cells. Rasha Aridi, Smithsonian Magazine, "Can Marine Mammals Catch Covid-19 Via Wastewater? The Evidence is Murky," 9 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

23 Jan 2021

Cite this Entry

“Infect.” Dictionary, Merriam-Webster, Accessed 25 Jan. 2021.

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More Definitions for infect


How to pronounce infect (audio)

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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