Uriel wasn't keen on keeping secrets from the general population as he could relate to them in more than one aspect, but just like in other occasions he had to admit it wasn't his call. Besides, it wasn't like he didn't keep almost all of his findings a secret from everyone, some even from his close friends.
The only thing that was left for them was to identify the source of the contamination and eliminate it safely, though Luna and Uriel being the only ones who knew the true extent of the infection also meant they were the only ones able to handle the situation leading to them going out into the woods by themselves.
If prions were frightening enough to affect Luna to the point of her emotions leaking out, then Uriel decided it was best to take matters seriously and he put on his glasses that allowed him to see flux energy.