infect
Americanverb (used with object)
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to affect or contaminate (a person, organ, wound, etc.) with disease-producing germs.
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to affect with disease.
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to taint or contaminate with something that affects quality, character, or condition unfavorably.
to infect the air with poison gas.
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to corrupt or affect morally.
The news of the gold strike infected him with greed.
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to imbue with some pernicious belief, opinion, etc.
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to affect with a computer virus.
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to affect so as to influence feeling or action.
His courage infected the others.
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Law. to taint with illegality, or expose to penalty, forfeiture, etc.
verb (used without object)
adjective
verb
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to cause infection in; contaminate (an organism, wound, etc) with pathogenic microorganisms
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(also intr) to affect or become affected with a communicable disease
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to taint, pollute, or contaminate
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to affect, esp adversely, as if by contagion
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computing to affect with a computer virus
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international law to taint with crime or illegality; expose to penalty or subject to forfeiture
adjective
Usage
What does infect mean? Infect is a verb that means to taint someone or something with disease-causing germs or to spread a disease to another living thing, as in The doorknob was infected with disease-causing bacteria. Infect can also mean to taint something in a way that negatively affects quality, as in The water was infected with toxic chemicals. Computers and other devices that connect to the internet can also become infected. Instead of a virus of living organisms infecting your computer, though, bits of code attack your computer system to do harm. Infect is also used figuratively to mean to corrupt something in various ways. It can mean something was corrupted morally, as in The constant flattery caused him to be infected with hubris. Infect can also be used to mean someone has been corrupted by harmful thoughts or beliefs, as in He allowed hatred to infect his mind. The adjective infectious is used to mean something is capable of infecting things, as in Doctors worked to stop the spread of the infectious disease. Infect can be confused with infest, which means to overrun a place or live there in an unwanted manner. Example: Tia stayed home from school so she wouldn’t infect her classmates with the flu.
Other Word Forms
Etymology
Origin of infect
1350–1400; Middle English infecten < Latin infectus (past participle of inficere to immerse in dye, discolor, taint, poison), equivalent to in- in- 2 + -fec-, combining form of facere to do 1, make ( see fact) + -tus past participle suffix
Explanation
To infect is to spread an illness to another person. If you sneeze on your friend, you may inadvertently infect her with your germs. When a disease moves from person to person, it infects them. Most diseases only spread within one species, although there are some, like avian flu, that can infect both humans and other animals. Another way to infect someone is to deeply affect them with an idea or emotion: "His enthusiasm for music infects the class with excitement." The Latin root, inficere, means "to spoil or stain" and "to dip into."
Vocabulary lists containing infect
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Ebola viruses normally infect animals, typically fruit bats, but outbreaks among humans can sometimes start when people eat or handle infected animals.
From BBC • May 18, 2026
They calculated that the virus’s infectiousness—an estimate of how many people one contagious person will infect on average—is 2.1.
From The Wall Street Journal • May 16, 2026
She did not infect anyone else after her return despite taking two commercial flights in the U.S. when sick and before she was hospitalized in Delaware.
From Los Angeles Times • May 14, 2026
They infect in different ways and are classed in entirely different phylums, meaning they are not remotely related.
From Salon • May 11, 2026
When he needed to buy eyeglasses, he let researchers infect him with malaria to study a new drug.
From "The Immortal Life of Henrietta Lacks" by Rebecca Skloot
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
