Your Guide to EV training!

Chance of three wilds is even lower. Upwards of one in ten trillion?

You get one pokemno with pokerus and you're set for life. Just infect it to some "pokerus mule" pokemon, set the mule in your PC after it's infected (pokerus won't leave when the pokemon's in PC), and get him out to infect any of your new pokemon when you want.

That's why it's much easier to simply go ask someone on serebii/smogon/etc to infect your pokemon.