Why do my Pokemon keep getting the pink smiley!

Question

People say its pokerus , but I know it cant be. My hoopa, deoxys, kyogre, latias, serperior and venusaur all have it, but do not and never have had pokerus. The ones that do: delphox, greninja, chesnaught, and dragalge, dont have the mark, recently the mark showed up on my kyurem and scizor, they did not have pokerus at all, I opened Pokemon and there the mark was, haunting me with its pink!
My snorlax, mewtwo and charizard recently were cured, but in a week the mark hasnt appeared.

I only want to know why it shows up, I cant get rid of it anyway.

Comments

It shows up after pokerus is over, so I'm pretty sure that all of your  pokemon with the pink smiley had pokerus at some point, you just may not have noticed

Answer 1

The only way to get that icon is for your Pokemon to have Pokerus.

You most likely didn't notice that your Pokemon had it before you realized the smiley was there. For Pokerus to cure, it takes anywhere from 1-4 days. Perhaps, in that timeframe, you didn't check your Pokemon throughly for the virus.

Comments

You know I was close to telling you a ridiculously long story, but while writing, I had figured the reason, and feel immensely thick for not thinking this sooner.
All the ones that have the mark, were traded. I can only assume that before I received it they got pokerus with a previous trainer, and were cured. I strongly think you're right, things tend to go over my head. Well... I'm dumb, actually, that's me normally.