The Plague of Undeath is what the Blood Fever variant has come to be known as. It was developed by the Totenkopfs after being extracted and mutated from Mordecai de Ardyn, and produces symptoms similar to the original virus, though it is much quicker and deadlier...and unlike the original Blood Fever virus, it affects all races. It also has the unexpected side effect of raising the dead as shambling, mindless undead. It was first released during the Third Battle of Remonton by Bishop Arbriel Conrad, and continues to ravage the country of Remon as it raises the dead who become warriors in Arbriel's ever-growing undead army, the Wretched.
Since the Remon outbreak, Totenkopfs have also been able to infect certain people in other kingdoms with the plague although thanks to the efforts of the Grand Alliance other kingdoms haven't experienced an outbreak yet.