Germ Theory of Disease is a theory in biology which tells us that diseases are not spontaneously generated but caused by micro-organisms / microbes, commonly known as 'germs'. These germs multiply to cause and aggravate diseases in living beings. This theory is taken to be the cornerstone of medicine and microbiological researches, leading to innovations in the field of anti-biotics.
It was Louis Pasteur who discovered that most infectious diseases are caused by 'germs'. He also invented the immunizing method, Pasteurization, named after him. Of course, in Atharvaveda, an old Hindu sacred text, it was told that diseases are due to living causative agents such as yatudhanya, kimidi, krimi and durnama.Since Pasteur and his successors like Koch and Flemming the theory has been a great contribution to modern medicine and microbiology, a refutation of the idea of spontaneous generation.