Don’t forget that when the young guy started to get accused of possibly spreading the sickness (Ch.14), he insisted it wasn’t airborne even though he had just admitted that there wasn’t anyone in the village who could study it. When they caught him on that point, he quickly changed stories and yelled about all of their crops failing and their guards getting scammed while approaching the throne without permission. His outburst pressured the emperor into letting him stay in the castle for a week while they gather information so he can make his decision. (Also, when he approached, the emperor immediately started to get a headache.)
I don’t think he’s an “innocent plague carrier.” It felt more like he was taking every possible step to spread the demonic corruption to the people in the room.