There is no definitive answer to this question unless someone says "I got one". sumwun would be correct, the developers would know better than to let someone put something to the likes of a virus into Wonder Trade. There would be outrage and terrible backlash if this base wasn't covered.
Anyway, I suppose I'd have to ask you what the extent of the hacks are. Why wouldn't you be able to trade them? Why would that be dependent on the number of individuals you have? If it won't hurt your game, you shouldn't be worried. You should in most cases be able to use them against NPCs.
I have gotten hacked shinies several times over; most of the time, they are from streamers who are doing giveaways to surprise people into following them. AusLove is a popular one, and I got my first one of these hacked shinies from him in Omega Ruby (shiny 6IV Empoleon). I've since received a number of high level 6IVs, sometimes shiny, the most recent example being a shiny English Victini which I still believe has been shiny locked since it was introduced.
To my memory, I have at least seven suspicious Pokemon from Wonder Trade, six of those were level 100, and five were shiny. I can list them if you'd like.
I don't know what you want from an answer, but I don't think there really is one besides that any hacked Pokemon that passed through Wonder Trade shouldn't be dangerous. I'm sure this was covered by Game Freak before their games came out.
