When does Pokerus start to apply?
I am attempting to keep track of EVs but am not sure whether 1) Pokerus starts doubling EVs for the battle during which it was contracted, or 2) It starts applying EVs afterwards.
For example, if my Larvesta contracts Pokerus after defeating a Whismur, does it obtain 1 HP EV or 2 HP EVs?
The pokerus is applied after the battle, when the EV are already distributed. Therefore, it won't gain additional EV from this battle.