not sure how i feel about it.
question: How will the game know the difference between infection vs. poison? they show up as the same counter. will this need a counter change to differentiate between poison and infection?
I think the card does a little much? it seems the way most decks that use infection work is they spam it to a lot of creatures (plague) and then u play this. It would, in many cases, if used right have more than 10 all the time. maybe consolidated the abilities? my suggestion is get rid of the locking ability part and just do the mini thorn shield for 0 to 10, and the mini thorn shield + damage for 11 +.