on an recent post, minoanon stated that the hotel has contracts put in place that prevent some types of organisms from reproducing and thus might cure certain illness. however, taking in consideration the labyrinth is built to torture, the valley may be capable to instill diseases upon him.
Ah! I hadn't see that post (I'll have to go find it now :D ) I suppose it makes sense that those contracts might prevent the Master and the guests of the hotel from getting sick, or lessening/ curing any existing sickness, but it would likely still harm Asterion considering the Labyrinth is meant for torture.
It's strange sometimes I forget that the Labyrinth is still meant to be torturing Asterion, because I get too focused on how it has become the Hotel, which is meant to be a place of healing for others (at least that is what Asterion is trying to turn the Labyrinth into).