There are many cases when you insert a flash drive and your antivirus program alerts you that you have a virus. It may be a false positive alert, but antivirus software have this behaviour because the USB stick it has an auto start process and your antivirus protects you from different files against start up without your consent.
You can easily disable the auto start-up or autorun.exe process running this small software. it does not need any installation, just run the executable file.
You can set it to automatically immunize all USB drives that are inserted in your computer or laptop.