infect

American  

[in-fekt] / ɪnˈfɛkt /

verb (used with object)

1. to affect or contaminate (a person, organ, wound, etc.) with disease-producing germs.

2. to affect with disease.

3. to taint or contaminate with something that affects quality, character, or condition unfavorably.

   to infect the air with poison gas.

4. to corrupt or affect morally.

   The news of the gold strike infected him with greed.

5. to imbue with some pernicious belief, opinion, etc.

   Synonyms:

   corrupt, damage

6. to affect with a computer virus.

   Synonyms:

   arouse, stir, touch

7. to affect so as to influence feeling or action.

   His courage infected the others.

8. Law. to taint with illegality, or expose to penalty, forfeiture, etc.

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verb (used without object)

1. to become infected.

adjective

1. Archaic. infected.

infect British  

/ ɪnˈfɛkt /

verb

1. to cause infection in; contaminate (an organism, wound, etc) with pathogenic microorganisms

2. (also intr) to affect or become affected with a communicable disease

3. to taint, pollute, or contaminate

4. to affect, esp adversely, as if by contagion

5. computing to affect with a computer virus

6. international law to taint with crime or illegality; expose to penalty or subject to forfeiture

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adjective

1. archaic contaminated or polluted with or as if with a disease; infected

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

• infectant adjective
• infectedness noun
• infecter noun
• infector noun
• noninfected adjective
• noninfecting adjective
• preinfect verb (used with object)
• reinfect verb (used with object)
• uninfected adjective

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."

Example Sentences

Animals traded through global wildlife markets are far more likely to carry diseases that can infect humans, and the risk grows the longer those species remain in circulation, according to a new study.

From Los Angeles Times • Apr. 13, 2026

The virus is so contagious that any misstep could kill the patient on board and infect the crew members, who would then be vectors to spread the deadly pathogens across America.

From The Wall Street Journal • Mar. 20, 2026

The spread of New World screwworm in Mexico, a parasitic fly that can infect livestock, adds another layer of uncertainty.

From Barron's • Mar. 5, 2026

While it is typically found among dogs, it can also infect big cats - often fatally.

From BBC • Feb. 23, 2026

And so every time an interesting new virus appears in the meat factories, the scientists take samples and craft them into viruses that can infect humans.

From "Legend" by Marie Lu

Related Words

• affect
• poison
• taint
• touch