Plague (Gone book #4), Michael Grant

Disease is spreading through the streets of Perdido Beach: a devastating, hacking cough that makes the sufferers choke their guts up – literally. Across town, Little Pete lies unconscious, struck down by the mysterious illness.

With the most powerful mutant in the FAYZ out of action, the future of the world hangs in the balance… The GONE series is Lord of the Flies for the 21st century. In turns breathtaking, harrowing, and utterly terrifying. Its complex characters and moral dilemmas will delight fans of The Hunger Games, Divergent and The Maze Runner.