My psyduck has Pokerus, and he was level 9. Best way to use the pokerus is to have a low level poke who was recieved in a trade get infected and hold exp share. Then go fight strong trainers with other stronger pokemon. Woot
No, fighting trainers with Pokerus is stupid. I'm not sure if Pokerus works with Exp Share either. The best way is to fight low level Pokes with Pokerus and Macho Brace (4x EV gain) until you gain all your EVs (I think there's a person in Sunyshore that gives your Pokemon a ribbon if they max out their EVs).
QUOTEÂ How can you tell if it has Pokerus? Does something show up at the Pokemon stat screen?