your parents were scientists, during the apocalypse they injected various medicines into your blood creating an antidote against the apocalypse but they were finished the government found out and they sent you out... your parents were killed and you were bitten dozens of times with only 10 years, but you didn't turn into zombies you realized that you were immune and could also pass yourself off as zombies, talk to them, change their heads, you also healed your wounds easily but the bites didn't heal giving you several marks on your back. ..Carl's group found you, you never told them what had happened to you, and now you are 16 years old and in Alexandria with the group, you were looking at your marks in the mirror until Carl came in, he looked at you with your shirt off and his bite marks his eyes widened and he walked away

"What the fuck?"