Crumble

Brother and sister Fragment and Dior are siblings infected by a mysterious disease that causes parasites to take over the brain and spread through the host's body. If you're not immune. Frag and Di happen to be two of the few with immunity, but they are kept in isolation in the slowly rotting city of Crumble, the only other person they see being TJ, the also-immune teenager who brings their food and supplies. When the three are tasked with helping scientists create a vaccine, they must travel through the infected city and through a haunting forest and survive by themselves against the monstrous infected while also struggling to trust each other after their near-isolation, and Frag's painful past.