Ok what are your opinions on the GEOSTIGMA virus or disease?

I personally think that is was a bit strange how there was no mention of it in the game and how it just suddenly turned up 2 years later

What also got me about it is that it was miracolously cured at the end of the film

The Geostigma reminds me of AIDS because it seems to slowly make the body weaker and weaker eventually leading to death.

I think it´s Jenova revenge on human kind, and just like she destroyed the Cetra she used Jeostigma to destroy humankind.

I actually thought it was the only good thing about Advent Children. Geostigma was a great turn of irony that really fits well with the original game - it gives the Lifestream alternate functions and savior and destroyer. Whereas Lifestream saved the population, it also infected them because of Jenova's thoughts.

My thoughts on Geostigma not being mentioned earlier? I think it may have not existed before the end of the game - perhaps Jenova didn't diffuse her thoughts into the Lifestream until the party defeats her before they defeat Sephiroth. Or perhaps, it might have existed, but misdiagnosed as a form of Mako poisoning (this would make sense, since the only way to get Geostigma is to get in contact with the Lifestream).

well I don't know what it is really, but one thing I don't understand is that what is it they see i nthe Geostigma? I have watched the film many times, but I can't figure out what it is they see or feel in the Geostigma

People get infected with Geostigma when they get in contact with the Lifestream, which is an occurrence which happens en masse at the end of FFVII. The reason for the infection is that Jenova's thoughts have been dissolved into the stream.

Hopefully this explains some of your questions.

Symptoms and Explanations:

Weakness, General Pain
The reason people are weakened and may die of the disease is due to the immune system trying to push Jenova out of the body. In trying to get rid of Jenova, it creates results similar to auto-immune diseases and other side-effects resulting from the attempted expulsion can occur.

Blackened Skin, Black Discharge
As the body attempts to expel Jenova from the system, people will find black viscous liquids, either seeping directly from the skin, or sometimes spitting it out, sweating it out, etc. When a person dies of Geostigma, they seem to "overflow" with this black liquid. This is examined more closely in the Case of Denzel.

Possession
Those afflicted with Geostigma have a similarity to the Sephiroth clones; they are biologically connected to Jenova. Thus, just like the clones, Jenova can call to them and possess them. This is seen in the black baptism scene at the Forgotten Capital, as well as a little bit later in the movie where all the children are gathered in the city square.

It did, thanks, I'm still kinda new to final fantasy but still I love it

Haha, Jenova-Herpes.