Help! How To Delete "rootkit.mbr.azusa.a"

Hello,

I have recently got a message from my Bitdefender total security saying it has detected a virus but it can't delete it. It comes up when I plug in my USB or my external hard drive. Obviously I want to get rid of it from my laptop and/or any other of my devices. I think it has infected laptop and my usb, how do I get rid of it.

Please help!