Originally Posted by Aralith
If the Jenova cells in his body were still active and he still had Geostigma, why wouldn't he have contracted it during the events that take place in the game. He still had Jenova cells injected into him, and yet no Geostigma. Remember, Jenova was even reawakend in the game (to an extent) by Cloud's presence. Unless you think it was just a coincidence.
Anyways, all I'm trying to say, is that as long as Jenova cells are active (i.e. being used to control you in Cloud's case), then you're safe from Geostigma. If not, as in the movie when Cloud had not been being controlled for two years, then Geostima presents. Once again, never stated anywhere, just my own theory. You don't have to believe it, but it makes pretty good sense to me.