What's Different About Huck?

Joseph: I haven't found anything consequential about this kid. Not as blood worked, not as check up, nothing. There has to be something. Maybe if I had better equipment or bigger sample size to work with. Next time there's a giant hum, we'll ask some people to stand outside and the ones who live can come see you after. That actually would help. What about Huck? What about him? We could leave him out there, exposed during the next one, monitor him. He says he's immune. But that's kind of... Didn't he also say that it feels like his brain is falling apart and that he might disappear?