Microbe - Sometimes referred to as a microorganism, a microbe is an organism that is microscopic and thus invisible to the naked eye. ⏎
Germ Theory - A theory in medicine stating that microorganisms are the causative agents of infectious, contagious diseases.⏎
Infection - The entry, establishment, and replication of pathogens inside a host organism.⏎
Mucous Membrane - The moist linings of body passages and internal cavities involved with absorption and secretion of substances.⏎
Immune System - The system of biological structures and processes that protects the body from foreign substances, including pathogens.⏎