Oh I'll have to dwell more on Haruki, and Dante (I have named them now >:) ) because rn they're just NPCs over fleshed out OCs.
So the zombie plague started a good decade or so from when kids are like 10-12 since that's when I usually focus on for Astra. So it's a mixed bag of kids who were born that way or were infected later. Kids who were born zombies are almost always Cognizant and lucid, but kids who were infected while they still have brain elasticity have a very high rate of retaining or regaining their cognizance. So they're just people who are also zombies.
That said, puberty can be kinda random and a lot more altering than normal puberty. Like Sloth, who just started stretching upwards and is becoming more gibbon shaped.
The zombies are created by a parasite that grows on the brain and spinal column and hijacks the entire nervous system. The parasite then starts hijacking the host's cells and repurposing them, while also spreading eggs throughout the host. The zombification process makes them ravenous and puts up their caloric needs drastically while the brain damage makes them disoriented and volatile, so they become cannibalistic. Adults don't tend to recover well and tend to stay as noncognizant zombies.
Most zombies were infected by EATING the eggs rather than being spread via biting. Zombies just shed infected flesh constantly, through coughing, biting, and disintegration, so they contaminated lots of water supplies after the initial panic and infrastructure collapse. Patient zero was probably a zombie in a water tower somewhere.
While most zombies incidentally infect, there are zombies who specialized in intentionally introducing the eggs directly into victims mouths. Neither noninfected and infected folks like them, since they eat other infected to increase their parasitic load. And then they just, uh, for lack of a better word put that zombie material into someone's mouth.
As for the kids survival, they're all living in cognizant zombie outposts scattered around the place. My OCS generally live on the US/Canadian border but I still haven't picked a state/city for them to live in. There's infrastructure now and the kids are either with their birth families or in makeshift adoptive families since everything's pretty hapdash after the zombie apocalypse. Kids go to school, help on farms, hunt deer since the deer population exploded, and learn trades and skills.
Astra migrated down from Canada where there's lots of uninfected folk still holding out. There's some begrudging tolerance from the zombie outposts and the noninfected outposts, because the zombies have access to everything and help keep other zombies away and the noninfected outposts up in Canada are locked in where it's cold enough that zombies are less of a problem. Since cognizant zombies are still zombies, they aren't able to be around noninfected folk because their zombie parasite overrides and tries to EAT. THEM. So they generally try to keep contact minimal and keep from smelling each other while exchanging.
