PBS just aired a great episode on The American Experience. It was about yellow fever. And how while the cure has not been found, the pioneering efforts of some dedicated doctors, in one case sacrificing his life, lead to the understanding that a certain type of mosquito was transmitting the virus. Then through screening, clearing out cisterns and sterilizing water to kill larvae, the epidemics were stopped. All of this happened in the early 1900s.
And what was The Watchtower Society saying 20 years later about the causes of disease? Note this little gem from the 1928 Golden Age:
*** The Golden Age, Nov. 28, 1928, p. 133 ***
All human ailments have their start in the intestines.