Answered so going to close. (Pokerus is a rare 'disease' in Pokemon that essentially lets them get stat boosts faster - it double their EV gains if you know about that. It can be spread to other Pokemon but loses that trait unless a Pokemon that has it is in the PC during every midnight. Spreadable Pokerus is mentiond by 'PKRUS' in a purple box on the status screen, and the face is for the non-spreadable form).
Ask questions in the Help thread sticky at the top of this section next time, please.