While employed as assistant to the professor of the maternity clinic at the Vienna General Hospital in Austria in 1847, Semmelweis introduced hand washing with chlorinated lime solutions for interns who had performed autopsies. This immediately reduced the incidence of fatal puerperal fever from about 10 percent (range 5–30 percent) to about 1–2 percent. At the time, diseases were attributed to many different and unrelated causes. Each case was considered unique, just like a human person is unique.
Semmelweis' hypothesis, that there was only one cause, that all that mattered was cleanliness, was extreme at the time, and was largely ignored, rejected or ridiculed. He was dismissed from the hospital and harassed by the medical community in Vienna, which eventually forced him to move to Budapest.
Semmelweis was outraged by the indifference of the medical profession and began writing open and increasingly angry letters to prominent European obstetricians, at times denouncing them as irresponsible murderers. His contemporaries, including his wife, believed he was losing his mind and he was in 1865 committed to an asylum (mental institution). Semmelweis died there only 14 days later, possibly after being severely beaten by guards.
I wonder how many similar ideas are being ignored or rejected today.