Germ theory of disease
Germ theory at the Health Care Museum
Germ theory denialism (pseudoscience), more, moreNote that germ theory, like the more complex theory of evolution, can't be proved directly. It makes useful predictions. Note also some diseases, for example metabolic diseases, aren't caused by microorganisms. This doesn't disprove germ theory. Note also that some diseases result from interaction of microorganisms with environmental conditions. Again this doesn't disprove germ theory.Germ theory led to the discovery of fungi, bacteria and ultimately viruses.
Pasteur's evidence against spontaneous generation was a key experiment supporting germ theory (don't confuse spontaneous generation with abiogenesis)
People who deny germ theory
Louis Pasteur and the origin of germ theory
Germ theory as a medical milestone
Germ theory at wikipedia
Koch's postulates are a set of rules for isolating microorganisms and proving that they cause disease. They remain useful for identifying and characterizing new disease agents.