The germ theory of disease was not really fully developed until the 1870s but, 30 years before this, a doctor in Vienna called Ignaz Semmelweis made a discovery that was very important but not accepted at all at the time. Semmelweis worked in a maternity hospital where the death rate of mothers and babies was extremely high because of an infection commonly known as child bed fever or puerperal fever. However, Semmelweis quickly made a very unpopular observation; he noticed that the ward run by midwives had a much lower death rate than a ward run by doctors.

At that time, doctors went from one patient to another without washing their hands, so the bacteria that caused child bed fever were transmitted easily around the ward. Semmelweis’ suggestion that doctors cleaned up between patients, and wore clean coats for the ward and different clothing for the room where post mortems were carried out achieved a huge drop in death rates. However, his claim that the doctors were doing a worse job than the midwives led to him being shunned by his colleagues and dismissed from his position.

After getting another job in another hospital, and making the same observations and improvements, Semmelweis was again heavily criticised and lost his job. He died (actually he was murdered by the guards) in 1865 in a mental institution, widely regarded as a madman, and never lived to see the theory that tiny particles, invisible to the naked eye, could carry infectious disease from person to person.

http://www.typesofbacteria.co.uk/how-when-were-bacteria-discovered.html

http://en.wikipedia.org/wiki/Ignaz_Semmelweis