What happened to my Pokerus on my Pokemon?

I already know it goes away but I had a Larvitar, a Gible, and a Abra, all get it around the same time and like a day and a half later (Garchomps and Alakazams was gone. But I had a Pupitar and it still has it and its been like almost 4 days. Does it disappear randomly or something?? or is it different with different pokemon??