I am no expert, though my Pokemon have it, but I know it doesn't do anything bad. I heard that it doubles a hidden stat called EP, or effort points. Please don't ask me what these things do, but they sound pretty good. I hope this answer helps, even if only a bit. :)
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Get a Pokemon with Pokerus and put the Pokemon you want to have it in the party with it. To transfer the PokeRus condition to other Pokemon, have the infected Pokemon in the party with the desired Pokemon and take it out to battle. After a few battles, most (or all) of the Pokemon will have contracted PokeRus.
The Pokerus is not a cheat, but a random status aliment that Pokemon can contract. Obtaining Pokerus is largely random, but can be spread by having a Pokemon with Pokerus in the party with other uninfected Pokemon.
A Pokemon can get Pokerus in any game. You can get pokerus by meeting a wild Pokemon infected by Pokerus. When you have Pokerus, all Pokemon that is with it (your party or a box etc. ) will also be infected by Pokerus. But if it is kept in your party, Pokerus will gradually go away. Your Pokemon does still does get boosted EVs however. if you want to have a pokerus in ur Pokemon that badly just use action replay code to get it... and if u want to remove it then just change your date like 5 days or more
If you get a Pokerus, then you're very lucky. So keep the Pokemon that you want to get the Pokerus spread to, and keep them in your party. As you travel, the Pokerus will gradually spread to all of the Pokemon in your party. Another great note - If you want every single Pokemon you have to get Pokerus, then keep one Pokemon with Pokerus in your PC Box. I think the Pokerus doesn't go away there, so you can keep on spreading Pokerus to every other!
Your Pokemon can catch PokeRus from battling a wild Pokemon which has it. There is no specific location as PokeRus is found with any Pokemon, anywhere Pokemon are found. No item will give or help your Pokemon catch the virus, just battle and hope you will get it.