The Pokerus Virus doubles stat experience
in G/S/C, and i think it's only in Crystal
, actually(don't quote me on that). If you ever get this virus, consider yourself lucky. It's like the chances of finding a shiny pokemon, or slimmer or something like that. A pokemon will be infected with this for one 24 hour period, at which point it clears up, forever, they will never be able to catch it again (
If you put the infected pokemon in a box, it won't lose the virus until you take it back out and let it stay in your party for another 24 hours. Basically, you can train with it all you like within that 24 hour period, deposit it, and the next day do it all over again. Make sure you don't forget it's in your party!
You can pass the virus on to any other pokemon in your party aswell by walking around for a bit with the infected one in your party with them.
Your best plan of attack with this Virus is to infect another pokemon and store it in the PC. This way, you always have the option of infecting any other pokemon you wish to train later on. JUST DON'T FORGET TO KEEP ONE IN THE PC.
~[end !CeMAn's PoKeRuS guide]~