Eggs can hatch with Pokérus. And I'm sure gift Pokémon would never get Pokérus (same for the NPCs and fossils, but I'm not sure. I think fossils are like eggs). I also don't think Pokémon you interact with can have Pokérus... But they are wild Pokémon. Does this mean the Necrozma from Sun/Moon can have Pokérus?
EDIT: I couldn't find any info on Bulbapedia.