nightcat said:It doubles your Evs earned.
The pokecenter lady will tell you about it, and after going there a certain amount of time, it'll go away.
To spread it, keep the infected pokemon in your party, and infect some drone, like an azurril or something. Put that in your PC, and it'll never go away. Just take it out when you want to spread it, then put it back.
~nightcat ;197;