What are some reasons the Pokérus icon will not appear?

However, I’ve been traded four Pokémon with a smiley. Confused, I tried spreading pokérus on my non-smiley Pokémon to see ifI̶ ̶w̶a̶s̶ ̶h̶a̶l̶l̶u̶c̶i̶n̶a̶t̶i̶n̶g̶ ̶t̶h̶e̶ ̶p̶o̶k̶é̶r̶u̶s̶I could spread it again, and it didn’t work. They also appear to gain 2x EVs, but I don’t know for sure. Out of 5-8 Pokémon that I’ve had with pokerus, only a few of them got the icon. Some of them were traded over, and others were Pokémon I spread to. None of the ones I’ve spread to by myself or that came with pokerus had it, only the ones that were already cured when they came to my game.

So, what are some known/confirmed reasons why the smiley icon will not appear? Is there some chance that it will not appear that I don’t know of, or is there something wrong?

Edit: Throwing inthis. Mew, Empoleon and Dianciehadpokérus. Wailordhaspokérus.

Pleaselog inorregisterto add a comment.

Did you get the Pokérus in question via a trade? If so, it’s entirely possible they might have sneaked the hacked strain #0 through the Transporter and somehow traded it to you. Strain #0 is a one-day strain that, after the one day ticks, leaves no trace that the infected ever had Pokérus. As the developers intend for a Pokémon infected to never be able to contract it again, they don’t make strain #0 legitimately obtainable.

This might be why, just asking did you get it from WT or a trade with a friend. If its from a friend then ask them if they have the same problem.

Source:http://www.gamefaqs.com/boards/696959-pokemon-x/68529369