While the flies were a visible and tangible problem when one did not have an outhouse or latrine installed, the real danger, as I stated before, was from hookworm infection, and the subsequent destruction of the productivity of those afflicted. To be sure, dysentery and cholera spread by flies were serious dangers. However, they presented themselves in a most obvious fashion, and medical care could then be given. Hookworm? Well, if you don't know you have something, you probably aren't going to go to the doctor just cause you're feeling tired and run down, especially if that's the only way you've felt your entire life.