Don't you mean version number (or variant) of the virus?
Just shoot me.. It is confusing what I had said.. I should have used a better example.. like Software version ie V2.3.4 as in a version Of Nero.. v5.5.10

so as varients of a virii come out you will have.. the original whih is renamed to dot a.. when the b version is identified..
as in ms blaster.. msblaster, msblaster.b etc..

is that better?

cheers