I am trading Pokemon in the GTS and I am wondering if you can lose Pokerus so I can "increase the value of a Pokemon." If you can't lose Pokerus in Pokemon does a lv 39 Jolteon with Pokerus fair for a lv 1 - 10 Riolu? If not a fair trade what would be fair then?
Assuming that you are playing a Gen 6 game (Pokemon Y/Pokemon X, or Pokemon Alpha Sapphire/ Omega Ruby) No a Pokemon should not lose it's pokerus of it is sent into the GTS. The ways to cure it is if
1. You go to the Pokemon center and get it healed.
2. If the Pokemon is left in your party and a new day starts (Any other day then when you last saved the game.)
Now Pokerus can go away from anywhere from one to four days.
As value goes, pokerus doesn't really add value to the Jolteon. Now of it's a competitive Jolteon, then yes your trade seems reasonable. I can't suggest a fair trade but I will offer you a Riolu if you want one. Hope this helps :D