You can make your usb drive or stick as it is being popularly called to be free from virus.

What most self executing viruses do is to create dubious instructions into auto.inf file which the autorun.exe file executes and it spreads all over ur system.
So all you need to do is to create a two empty folders with the file names autorun.inf and auto.exe andsave them in your flash drive or any Pdas you use.
By doing this,you have effectively blocked the creation of any files bearing such names to ever be allowed on your flash drive.Why you might ask?

The answer is simply, no two files with the same file name can stay on a system in the same drive.

That is why when you are copying a file into a drive which has a file with the same name,it will ask you whether yu want to replace it or not.

Even on phone u cannot save two contacts with same name.So you are protected to 60 per cent of the viruses in the world.