look heres what ill do, you trade me any pokemon, it could be a magikarp, you just need that pokemon to be infected because its contages, you trade it to me, i infect it, (if its let out of the box for like 3-4 days in your team the desise is gone and that pokemon is imune to it BTW) i trade it back to you, and you let it spread to the rest of any pokemon you want, but the infection will not spread to the rest of your team unless it has been batteling which means if you let me infect a magikarp you have to batle with it(might be "hard" but you only have to win the batle to another magikarp) with other pokemon on your team exposed to the desise now. K?