Puerperal fever (or childbed fever) was common in mid-19th-century hospitals and often fatal, with mortality. In Vienna (General Hospital), childbed fever was taking many women's lives who had a baby in hospital. Nobody really understood why this was happening.

In 1860 Semmelweis  published his second essay named “The Difference in Opinion between Myself and the English Physicians regarding Childbed Fever”ospitals and often fatal, with mortality. In Vienna (General Hospital), childbed fever was taking many women's lives who had a baby in hospital. Nobody really understood why this was happening. Semmelweis rapidly recognized not only therapy was unsuccessful but also, based on some clear observations, the accepted etiology of childbed fever could not possibly be accounted for.  

In 1860 he published a book of his findings in childbed fever in 'Etiology, Concept and Prophylaxis of Childbed Fever'. In his book he explained his theories on childbed fever the ways to avoid spreading it by means of vigorous hand-washing.

Despite various publications Semmelweis' practice only earned widespread acceptance years after his death, particularly when Louis Pasteur confirmed the germ theory

Such a scientific explanation was only made possible some decades later when the germ theory of disease was developed by  Louis Pasteur and Joseph Lister and others.