Antivirus are small software programs that hopefully will spread from one computer to another and to interfere using computer operation.
A disease might.. corrupt or delete data on your desktop, use your e-mail process to spread itself to help other computers, or even erase everything on the hard disk.
Antivirus are often spread just by attachments in e-mail information or instant messaging messages. That is why it is critical that you never open e-mail attachments until you know who it’s from and you just are expecting it.