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:
The researchers say the novel viruses can’t infect humans and the technology could ultimately benefit us by protecting people against drug-resistant bacteria.
From The Wall Street Journal ● Aug. 9, 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
Three major Ebola viruses are known to infect humans, and researchers believe fruit bats are the natural source.
From Science Daily ● Jun. 22, 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
It uses a common cold virus that infects chimpanzees that has been genetically modified to make it safe.
From BBC ● Jul. 13, 2026
The U.K. also announced sanctions against hackers responsible for Lumma Stealer, malware that sucks up sensitive information from devices it infects.
From The Wall Street Journal ● Jul. 13, 2026
The species, named Taczanowskia waska, represents the first known example of a spider mimicking the appearance of a fungus that infects spiders.
From Science Daily ● Jun. 17, 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
Alison Fuller from Epilepsy Action said it is a "scandal" on par with infected blood and Post Office Horizon scandals.
From BBC ● Aug. 11, 2026
Most scientists believe that exposure to an infected animal is a more likely origin for the pandemic.
From BBC ● Aug. 6, 2026
People become infected by breathing in the contaminated air or touching the infected surface and then touching their eyes, noses or mouths.
From Los Angeles Times ● Aug. 6, 2026
Symptoms develop more slowly, allowing infected patients to remain well enough to move around and spread the virus before becoming severely ill, according to Corri Levine, a virologist at the University of Texas.
From The Wall Street Journal ● Aug. 6, 2026
He was weak and his infected leg was in excruciating pain from the stress and exertion he had endured the day before, hunting for Julio.
From "Death on the River of Doubt" by Samantha Seiple
A city-commissioned inspection report found that waste and high temperatures at the warehouse could speed up the breeding of flies capable of infecting wounds in both people and animals, a local NBC affiliate reported, external.
From BBC ● Aug. 9, 2026
This week government agencies linked Taylor shredded iceberg lettuce—served at Taco Bell locations—to cyclosporiasis illnesses infecting thousands of people in five states.
From The Wall Street Journal ● Jul. 18, 2026
When H5N1 bird flu began infecting U.S. dairy cattle in early 2024, veterinarians struggled to identify the cause.
From Science Daily ● Jun. 23, 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
His manner of speaking was infecting me, making me pompous.
From "Grendel" by John Gardner
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.
