Geostigma

A fictional disease created by Square Enix in the CGI movie, Final Fantasy VII: Advent Children.

In the ending FMV of Final Fantasy VII, the player sees the Lifestream sweeping throughout the planet (particularly in Midgar).

However, it is revealed in Final Fantasy VII: Advent Children that Jenova had contaminated the Lifestream. As a result, people were exposed to Jenova's cells as the substance swept throughout the planet. This caused the epidemic, Geostigma.

Geostigma is characterized by black scars that ooze of a black pus, all while causing the infected one mental illness, pain, or even death.

The disease was exposed a majority of the children throughout the planet. Two of the major characters in Final Fantasy VII: Advent Children, Cloud Strife and Denzel carry this disease, and suffer tremendous pain throughout the movie.

In the end, though, Aeris Gainsborough performs her final limit break, "Great Gospel," which summons a holy rainfall, eliminating Geostigma permanently.