The infected Pokemon will have the Pokerus virus for one day to four days, depends really. To infect other Pokemon, you need to put the contagious Pokemon in your party with the ones you want to infect and fight wild Pokemons for a few times and they will have the Pokerus virus. Once infected you can keep them in the PC and they will stay infected unless you take them out after a day or so they won't be infected anymore, but they still can get the bonus EV etc.
I'm online now, what Pokemon do you have? I would really like Pokemon from the earlier gens if you have them.