Basically...
With Pokerus, it just makes the Pokemon's stats go up faster, and there is something about Effort Points(whatever those are, go check Serebii.net). I one time had a Magikarp with Pokerus, so I gave it an Exp. Share and see what would happen(because I was training another one as well, to see the difference). In the end, Oddly enough, (never seen this before), my Pokerus Magikarp, once it got to Lv. 97, it said, for all the stats, +0. All of its stats were around 250, except for speed, which was aroun 350. My other Magikarp was still in the 100-175 range. And, Pokerus does go away, so you should always have at least one pokemon in your PC with Pokerus. It spreads, so technically, you could make every single Pokemon in your PC have it (it only spreads in your party).
And also, Pokerus does remind me of Toys R' Us, now that you mention it...