I won't. My friends are sick, too. I ain't gonna leave 'em.
It's the body reacting to Jenova cells. Jenova's kind like... um. A virus, in a way, I guess. I dunno, I'm no scientist, but I know it's just gonna get worse, and it's gonna kill people.
Aerith was a Cetra, so she could do something with the water to heal people. That's all I know.