English Reference
verb

infect

v.
US /ˌɪnˈfɛkt/ UK /ɪnfˈɛkt/ in·fect UK spelling infecting, infects

  1. 01 B1 Intermediate Medicine

    to pass a disease or bacteria to a person, animal, or plant.

    to contaminate a living organism with a pathogen, causing the onset of illness or disease.

    Simple

    The flu can easily infect everyone in the office if people don't stay home.

    In context

    Public health officials were concerned that the new strain might infect a significant portion of the population before a vaccine could be distributed.

    disinfectimmunize
  2. 02 B2 Upper Intermediate Computing

    to pass a harmful program or virus to a computer or a file.

    to corrupt a computer system or data file by introducing a virus or malware.

    Simple

    Be careful not to open suspicious emails, as they could infect your laptop.

    In context

    The malware was designed to infect the entire corporate network by exploiting a vulnerability in the outdated server software.

Usage infect bacteria

The resulting 16 novel viruses were created to infect bacteria and pose no threat to people.

BBC News· 6 Aug 2026

It uses a common cold virus that infects chimpanzees that has been genetically modified to make it safe.

BBC News· 13 Jul 2026

Etymology 1

From Middle French infect, from Latin infectus, perfect passive participle of inficiō (“dye, taint”).

Etymology 2

Borrowed from Latin īnfectus, equivalent to in- (“not”) + factus, perfect passive participle of faciō (“to do, make”).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Level C1 · Advanced
Frequency Frequent
Updated