[Do the vampires from Fevre Dream really need to drink blood to survive?]
Unlike the undead of myth (and many other novels), my "people of the night" could actually eat normal food, and it was that which provided most of their sustenence. The red thirst was more of an overpowering sexual urge that an actual thirst or hunger. Failing to satisfy it might drive them mad, but would not kill them. (They were very hard to kill in any case).