Hi. I have the same problem as the first poster.
I have the BF version. I had no intention of buying medicine 3 until I got a master healer for a chief, but an event in the game gave it to me. Now my healer is living his second life and getting nowhere as no one is getting sick. They just get old and die.
I have never seen a poison frog. Will they show up or should I start over?

You cannot get to chapter 2 without a chief.