thats weird, you're supposed to gain an additional 4 EVs arent you?
Say you got Patrat
Patrat gives out 1 atk EV
Power Bracer adds 4 more EVs(aka 1 extra attack stat at lv100)
So now you 5atk EVs. So 4 Patrats will give you 20EVs or 4 extra stats at level 100
Pokerus doubles the outcome of each battle, so you 10 instead of 5
It adds after every battle not level up in BW
I thought that was only after it hit 100.