Miss
It's not really my place, or anyone else's other than theirs or their guardians, to look into that kind of thing. To me, that feels a little like telling someone that if they're aware that they're infected with AIDS, then they have to tell everyone just in case someone might be around them if they happen to bleed openly. They know what's wrong with them and take on the responsibility just like any other person with a potentially or definitely contagious disease does when they're in public, you know?
And that's if they're from that exact world. There's plenty of zombie apocalypse fiction out there. I can't confirm if that's their world or just one like it; it's just the only one I'm familiar with because I've seen the show, so I sort of assume, I guess?