NovaBrunswick
Canada Connoisseur
I usually get it by trading for an already infected Pokemon but the one and only time I found a Pokerus randomly in the wild was around 3 years ago when I replayed my White 2. I was training my Pokemon in the Virbank Complex for my upcoming Virbank Gym battle and when I went back to heal in the PC, Nurse Joy told me that my Pokemon were infected with Pokerus.
What Pokémon was it?