pokerus is a virus that your pokemon may have if your battling other pokemon, if your pokemon have it will increase the EVs gain at the end of the battle,thus it is good to have if your training a certain pokemon, but if your pokemon has it it can lower your pokemon's happiness , but remember the odds of getting pokerus is very low if you have one it can spread in your entire party, but it wears off so remember to keep a pokemon who has PKRS in the pc, and also remember if your pokemon had it but you did'nt know check your pokemon's summary if there is PKRS then it still have it,how can you know if your pokemon had it before? but you did'nt know, check it's summary if you see a face sorta like a smiley on your pokemon's picture then it had it before but it is now immune
