Well, I'm pretty sure that infected eggs are found anywhere that normal eggs are. I think it's just a random chance that whatever egg you find will be infected.
I now have two infected ones. One I got literally right here. The other was another Pokémon catching forum. Can't remember which page
But Did Anyone Know How Many Level Did This Need To Be Hatch? Same LEvel As Odd Egg? By The Way, I Found One In Q And A Thread Today.