It's impossible for me to say I'm completely sure. The symptoms you saw out of some of your fellow Apprentices are only come of the possibilities.

Most times it's known for derailing inhibitions, morality, sanity-- and some are more affected than others. But there are also extreme cases like my brother's that appear dormant. He's in a coma. As it was explained to me, he is fighting the disease, but neither he nor it are strong enough to beat the other. Maybe he just shut down to stop it...

But I can't imagine a case where it doesn't show in some way or another.

[He doesn't even want to think about it.]

That is the best case scenario, but you're wise enough to know that's not always the case in reality.