The Legion has fielded men and women like me for centuries in combat. We were lucky, or perhaps the unfortunate few that somehow survived the change. We know that humans are the ones who react to the bites and scratches inflicted by a cat or dog and change.
The animal that infects us is just that: the vector. The animals themselves are immune to whatever it is. The human side gains a beast, a monster, or something else. Some believe it just awakens a dormant, sleeping, more primal, animalistic side of those afflicted.
Whatever it is, It certainly makes me more physically skilled, tougher, harder to kill, and hit harder. Still, its true strength is not what it adds but what it steals from me: Morality. A conscience. It banishes fear. Removes doubt.