Yay, lucky you. Yes I have pokerus too and it does double your evs, the effect lasts forever but you cant spread it to other pokemon after four days of infection.
I suggest you infect a pokemon and leave it in your PC. When you put it in the PC the four days are restored and dont count down as long as it's in the PC. That way you can withdraw it later, infect another pokemon, and then put it back in the PC.
Give an infected pokemon the Macho Brace and you'll gain x4 the normal amount of evs!