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
"For reasons we don't understand, HIV really wants to use CCR5 receptors to infect cells," Sacha said.
From Science Daily ● Aug. 13, 2026
It is possible that one day, he said, someone will use a similar approach to make viral proteins or viruses themselves that infect people and evade vaccine protection or natural immune responses.
From The Wall Street Journal ● Aug. 7, 2026
They were then refined to produce a type of virus, known as a bacteriophage, which infect only specific species of bacteria.
From BBC ● Aug. 6, 2026
Some farming populations make it even easier for their own fecal bacteria and worms to infect new victims, by gathering their feces and urine and spreading them as fertilizer on the fields where people work.
From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond
The virus that sparked a global pandemic still regularly infects, disables and kills hundreds of people per week.
From Salon ● Aug. 6, 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
It normally infects animals, typically fruit bats, but outbreaks among humans can sometimes start when people handle infected animals.
From BBC ● Jul. 2, 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
Engineered pollen blows just as easily as the original kind and infects all traditional plants in its path.
From "The Adoration of Jenna Fox" by Mary E. Pearson
Flea-borne typhus is an acute febrile bacterial infection caused by Rickettsia Typhi bacteria, which is spread by infected fleas often found on pets and wildlife.
From Los Angeles Times ● Sep. 24, 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
Doctors later reassured her she would keep her vision, but her face was badly infected.
From BBC ● Sep. 23, 2026
The virus spreads through direct contact with infected bodily fluids.
From Science Daily ● Sep. 20, 2026
Unlike Civil War surgeons who used antiseptic chemicals after a wound became infected, Lister's goal was to kill microbes in wounds before they caused an infection.
From "Ambushed!" by Gail Jarrow
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
“We need to get sick people out of their communities as fast as we can. We are doing our best to work with local leaders; otherwise, they will continue infecting others,” he said.
From The Wall Street Journal ● Aug. 6, 2026
Before the virus was identified, it spread from herd to herd, infecting cattle and contaminating their surroundings.
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
In Europe, Asia, and Africa smallpox became a constant, terrible presence, infecting almost every child, killing many and leaving others with the disfiguring pockmarks that are its telltale sign.
From "1491" by Charles C. Mann
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.
