[@PrinceAlexus] They do all need to breathe and have a heart beat, etc. They died and came back to life, but they are alive. I think the level of oxygen or number of beats per minute their heart needs to live will vary depending on the type of blight born they become since it can be wildly different person to person. It'll be less than what is required for a human in most cases though. 

However, they no longer need to eat human food and can only live by draining whatever is required for the type of blight born they became. I think Kira, for example, will even get sick if she eats regular human food now haha