Still, it's a sacrifice creature. Let's assume that Infection costs 2, due to Parasite. If that is the case, then the "Virus" card itself, due to sacrificing, gets a -1 cost.
Now, Blessing costs 3, but I'm a little anxious to say that an extra +1|+1 warrants a whole point increase.
So far, the numbers say that this thing should cost 4 unupped, and 6 upped. IDK, but since it's practically a spell (one-time use) I think we might be able to add in a new feature to OT's formula: Spell Creatures. Creatures that have abilities that cause them to only be able to use it once.