Can a thumb drive be infected with a virus?
Yes. Anything connected to your computer that is writable, including a thumb drive, can be infected with a virus or other malware. These types of media are capable of spreading the virus to alternative drives.
If a flash drive became infected with a virus, any computer that reads the drive could also become infected with the virus.
However, if you're running an antivirus program, it should detect the virus before it's transferred to your machine from the thumb drive. If you're concerned that a thumb drive is infected, it can be scanned for viruses like any drive on your computer.