Pokerus doubles the EVs you get when you KO a wild Pokemon.
So for example - if a Mareep usually gives 2SpA EVs, a Pokemon with Pokerus will get 4SpA EVs.
So for your Togetic, if you KO a Pokemon that gives 2SpD EVs (like Grumpig) while holding a Power Band and Togetic has Pokerus, you will get 12 SpD EVs. ([2+4]x2)
Source - Bulbapedia and experience