I don't know if it's intented to work like that so..
With a broken leg, I was just reaching the Healthy state after been hit by a zombie. Then another one came to me and killed me with only one punch !
http://www.youtube.com/watch?v=lVnZdlKf7hk
I came back 5 minutes later, my body was there with a broken helmet !
Do zombies really have the possibility to kill like that ? Or is that a default in their combat mechanic ?