With computers, infect describes an instance where malicious software is installed onto a computer or other device without a user's knowledge. For example, someone may install software on a computer that's infected with a virus. Once installed, the program would work as the user intended. However, the virus is also installed at the same time. Once a file is affected by malicious software, it's known as an infected file and can infect other drives and computers accessible to the user. Cleaning an infected computer requires a user have antivirus software with the necessary instructions required to remove the virus from all affected files.
The term "infect" may be used with any malicious software that gets installed on a computer, including adware, malware, spyware, Trojan horses, and worms.
What can be infected?
Generally speaking, whenever data is being transmitted it can put a device at risk. For example, an infected USB thumb drive could send malware to your computer and vice versa.
Can a human be infected with a computer virus?
Most humans have no software running inside them that's writable by a computer, which means a human cannot become infected by a computer virus. However, if you have a biological device like a pacemaker that's accessible and writable by a computer, it could be infected.