Dragonsblood By Todd McCaffrey

A mysterious epidemic is striking dragons, and the next deadly cycle of Threadfall is only days away. Somehow, dragonrider Lorana must find a way to save all the dragons—including her own beloved Arith—before they succumb to the sickness, leaving Pern undefended. No doubt the first colonists, who originally bred the dragons, possessed the advanced technology to find a cure. But over the centuries, that knowledge was lost.

Five hundred years in the past, a scientist foresees that a disease may ultimately destroy the dragons, and she is determined to find a way to change the future. Now two brave women, separated by hundreds of years but joined by bonds transcending time, become unknowing allies in a desperate race for nothing less than Pern’s survival.