>>58470824
Joking aside, "Disease" would be an interesting condition that would force you to use a Pokémon Center. Unlike poison, it can't be cured with a potion. It also gives Nurse Joy a real purpose. In the adventure, it would force the player to better plan their travel between cities.
Now, how would it work? The affected Pokémon would start each battle with its stats reduced, as well as passively losing HP. Worse still, Pokémon surrounding the infected Pokémon could become infected.
Would you be willing to release a Pokémon to save the rest of your team? To make the decision even more difficult, a sick Pokémon can't have items removed, so if it had a Mega Stone or any rare item, it's a complete loss.
