Geostigma

History
The earliest mentions of Geostigma come from Cetran texts which refer to a mysterious disease known as "the wound of the earth". Originally scientists thought this was referring to the Northern Crater. Popular opinion now is that this is the mysterious plague that wiped out the Cetra as a species.

Illness
Geostigma, in layman's terms, is the human body's inability to cope with Jenova's cells. If the body does not accept Jenova's DNA (ie: adult women), then the body's immune response is triggered. However, because the body is essentially combating a parasite, it requires much more energy and strength than is possible for the body to generate. The victim does not die of infection so much as exhaustion and related complications. At present there is no treatment or cure.

Symptoms
Victims of Geostigma exhibit a high fever, nausea and vomiting, and a distinctive muddy-brown rash that appears in splotches on the skin. The wider the rash has spread, the lower the chances of recovery. Most victims die of the illness. Only a handful of cases have ever survived, and these only because they had other factors guarding their health, such as the presence of a summon materia within their body. Examples include Vincent Valentine and Felicia "Elfe" Verdot.