I was at the Pokemon center and Nurse Joy said something like "Oop! It looks like your Pokemon has been infected by a microscopic organism. It is harmless, but annoying. I will get rid of it!" Thats not exactly what she said, but it was something like that. Why did she say that?
It's an incredibly rare with a 1 in 21,845 chance of encountering a Pokemon with it! You my friend, are incredibly lucky. It doubles the EV gain from battle. It spreads to different Pokemon as you walk around so my advice? Store it in your PC and keep it safe for competitive training! Do not get rid of it!
Hope this helps!