Hey, I've always thought that! I'd always heard of people moving to the mountains for the summer. I think their reasoning at the time was to get away from the "bad air" that brought on the Malaria. Back then they didn't know that the mosquitoes were what was carrying it.
Classic example which you may enjoy reading (I'm a big Kipling fan, and this is from what I think may be his very best book, Rewards and Fairies): A Doctor of Medicine.