Early evidence of microorganisms causing disease

As early as in 1813 there was evidence that specific fungi can cause diseases of wheat & rye, and in 1845 M. J. Berkley had proved that Potato Blight was also caused by a fungus. There was an incidence of “Great Potato Blight” in Ireland, which was a natural disaster that has immense effect on Irish history. So the importance of these diseases cannot be overlooked. Not only plants, fungal disease of animals were also in picture and in 1836 A. Bassi of Italy had shown the cause of certain silk worm disease was fungus. And few years later J. L. Schonlein showed that fungus can also cause skin disease to human. But unfortunately these discoveries fail to make medical science believe that microorganisms are responsible for major infectious diseases of humans. Actually they underestimated the capacity of microorganisms due to its small size. Everybody thought that an organism as small as bacteria cannot make much harm to a much bigger animal like human.