infect
Americanverb (used with object)
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infects,
present (3rd person singular)
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infected,
past participle, past
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infecting
present participle
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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)
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infects,
present (3rd person singular)
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infected,
past participle, past
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infecting
present participle
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
Derived Forms
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infectednessnoun
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infecternoun
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infectornoun
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preinfectverb (used with object)
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reinfectverb (used with object)
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infectantadjective
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noninfectedadjective
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noninfectingadjective
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uninfectedadjective
Inflected Forms
Participles
Conjugated Forms
Present
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infectsimple
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infectssimple
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have infectedperfect
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has infectedperfect
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am infectingprogressive
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are infectingprogressive
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is infectingprogressive
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have been infectingperfect progressive
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has been infectingperfect progressive
Past
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infectedsimple
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had infectedperfect
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was infectingprogressive
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were infectingprogressive
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had been infectingperfect progressive
Future
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.
See Examples For:
“Their lifespan is determined by humidity, so if you have humidity, the infected mosquitoes will live longer and infect more people.”
From Los Angeles Times ● Sep. 22, 2026
The resulting 16 novel viruses were created to infect bacteria and pose no threat to people.
From BBC ● Aug. 6, 2026
Already, mosquito-borne diseases kill more than 1 million people and infect about 700 million worldwide each year.
From Slate ● Aug. 4, 2026
Unlike bacteria that cause other food-borne illnesses—like salmonella and E. coli—cyclospora don’t infect animals, according to Dr. Ewen Todd, a food-safety consultant and adjunct professor at Michigan State University.
From The Wall Street Journal ● Jul. 17, 2026
The idea is that about 15,000 years ago a chance mutation let the virus “jump the species barrier,” as scientists say, and infect human beings.
From "1491" by Charles C. Mann
The virus that sparked a global pandemic still regularly infects, disables and kills hundreds of people per week.
From Salon ● Aug. 6, 2026
According to the study, this is the first documented case of a spider imitating a parasitic fungus that infects other spiders.
From Science Daily ● Jun. 17, 2026
It uses a common cold virus that normally infects chimpanzees but has been genetically engineered to make it safe for people.
From BBC ● May 22, 2026
The contagion is typically found in rodents and rarely infects humans.
From The Wall Street Journal ● May 7, 2026
Provided that each victim thereby infects on the average more than one new victim, the bacterium will spread, even though the first host happens to die.
From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond
Injecting antibodies can help provide temporary protection against a virus or, if already infected, help the immune system fight it off.
From The Wall Street Journal ● Sep. 28, 2026
Doctors later reassured her she would keep her vision, but her face was badly infected.
From BBC ● Sep. 23, 2026
Because indeed, patient zero—which refers to the first person to be infected with an illness or disease in an outbreak—is a loaded term.
From Slate ● Sep. 23, 2026
About a third of all infected persons reside in East Los Angeles, with other cases reported in the San Fernando Valley and South Bay, according to the recent epidemiology report.
From Los Angeles Times ● Sep. 22, 2026
I don't have a moment to wonder how on earth this rich man could have become infected.
From "Dread Nation" by Justina Ireland
Before the virus was identified, it spread from herd to herd, infecting cattle and contaminating their surroundings.
From Science Daily ● Jun. 23, 2026
In an interview with the Reuters news agency, Gaston urged the child and her mother to go to a health centre, as they risked "worsening their health" and "infecting their relatives".
From BBC ● Jun. 17, 2026
Even with this early identification, the outbreak spiraled into the deadliest Ebola epidemic in history, infecting over 28,000 and killing over 11,000.
From The Wall Street Journal ● May 22, 2026
With hantavirus, the incubation period can take up to six weeks, so people must be isolated for a really long time to ensure they won’t get sick and start infecting others.
From Slate ● May 16, 2026
Currie agreed that there was a terrible fever infecting the city, but he simply did not think it was yellow fever.
From "An American Plague: The True and Terrifying Story of the Yellow Fever Epidemic of 1793" by Jim Murphy
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.
