The Atlantis Plague (The Origin Mystery, Book 2) by A.G. Riddle

Atlantis Plague

From Amazon:

In Marbella, Spain, Dr. Kate Warner awakens to a horrifying reality: the human race stands on the brink of extinction. A pandemic unlike any before it has swept the globe. Nearly a billion people are dead–and those the Atlantis Plague doesn’t kill, it transforms at the genetic level. A few rapidly evolve. The remainder devolve.