Players should be infected as soon as they spawn or if an infected hurts them with his infected hands (or if you eat your infected buddy ^^). Survivors would have to find a cure in a limited time (one day, the dayz) before becoming a zombie. The cure should spawn in medical buildings or a special military lab in the north west (as far from spawn points as possible). I think it will help cooperation and will increase player's stress and immersion.We would have to think twice before fighting zombies bare hands, and before killing somebody on sight and risking to ruin the cure!!