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 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 issue is further complicated by bacteriophages, which are viruses that infect bacteria.
From Science Daily ● Jul. 17, 2026
The virus, therefore, could infect the lungs on contact.
From "The Hot Zone" by Richard Preston
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
It infects the heath-star moss that is damaging UK environments by taking over and turfing out other species.
From BBC ● May 30, 2026
The contagion is typically found in rodents and rarely infects humans.
From The Wall Street Journal ● May 7, 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
Both Wilcox and Edwards point to a wider pattern stretching from Aberfan and Hillsborough to the Post Office and infected blood scandals.
From BBC ● Aug. 10, 2026
Most scientists believe that exposure to an infected animal is a more likely origin for the pandemic.
From BBC ● Aug. 6, 2026
An infected person can spread the disease up to four days before a measles rash appears and up to four days after the rash appears, according to the county department.
From Los Angeles Times ● Aug. 6, 2026
“When a strain is less virulent, as in the case of the Bundibugyo strain, infected people feel sick, but not sick enough to be bedridden or abandon their daily routines.”
From The Wall Street Journal ● Aug. 6, 2026
A doctor diagnosed severe anemia and infected tonsils.
From "Votes for Women!" by Winifred Conkling
Rather than primarily infecting the lungs, H5N1 caused severe infections in the udders while leaving the respiratory system largely unaffected.
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
Many residents hide sick relatives from health workers, inadvertently infecting themselves through contact with the sweat and blood of the ill.
From The Wall Street Journal ● May 26, 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
Suddenly, people who might have been infectious for a week before getting treated were now going around infecting others for two or three or four weeks before they got cured.
From "The Tipping Point" by Malcolm Gladwell
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.
