The germ theory of disease is a scientific theory that suggests microorganisms, such as bacteria, viruses, fungi, and protozoa, are responsible for causing infectious diseases. Synonyms for the germ theory of disease include the microbial theory of disease, the pathogenic theory of medicine, and the contagion theory. These terms emphasize the idea that diseases are caused by the presence and growth of specific microorganisms, which can be transmitted from one individual to another. The germ theory of disease revolutionized medicine and paved the way for the development of vaccines, antibiotics, and other modern medical treatments that have saved countless lives over the past century.