Thank you very much for the reply.
I managed to use the level editor and I included all the diseases. Also if I schedule an earthquakes, random earthquakes won't happen anymore. So I schedule one for 30 months ahead and nothing happens till the month number 30. The problem is that after the scheduled earthquake, random ones start to happen again. My hospital was destroyed in a couple of months, even having a lot of handymans and I'm personally taking care of it. Earthquakes really ruin this game.
Which is the last map of your campaign? In the last map there are also epidemics (contagious diseases)?
The only bad thing about Four Corners is that there are no heliport.