Telluria (Telluria, #1) by Jodi Trask

SPFBO6

The earth was on the brink of a futuristic utopia when a new and deadly disease threatened to wipe out humanity. Telluria slowly dissolved its victims into one of the four primordial elements of water, fire, earth or wind. Terra was a child when her parents caught Telluria. The corporation New Atlantis developed a cure and distributed it for free just in time, saving her parents and the world from extinction. The world was just beginning to rebuild when Terra caught Telluria herself. She planned to simply go get the cure, but when her best friend Grey is killed by New Atlantis officials for trying to warn her against it, Terra is on the run for her life and the truth.