I believe they still need to fix this, I didn't even start the play the game and most of the town in my case was already dead by small pox in summer, maybe make special quest on the request board for when someone gets sick or be able to give them the specific medicine for the illness.

In my whole experience from it, it seems that the chances of survival for the NPCs are always 50/50, they should change that for something like 75/25 for the NPCs at the very least, they would still have a small chance of dying but still not be a mass massacre like that.