Microbe - Sometimes referred to as a microorganism, a microbe is an organism that is microscopic and thus invisible to the naked eye. ⏎
Immune System - The system of biological structures and processes that protects the body from foreign substances, including pathogens.⏎
Interferon - A type of protein produced by cells of the immune system that help keep viruses, bacteria, and cancer cells from growing.⏎
Infectious Disease - A type of illness caused by a pathogenic agent, including viruses, bacteria, fungi, protozoa, parasites, or abnormal proteins known as prions.⏎
Germ Theory - A theory in medicine stating that microorganisms are the causative agents of infectious, contagious diseases.⏎