Germ Theory - A theory in medicine stating that microorganisms are the causative agents of infectious, contagious diseases.⏎
Immune System - The system of biological structures and processes that protects the body from foreign substances, including pathogens.⏎
Infection - The entry, establishment, and replication of pathogens inside a host organism.⏎
Morbidity - The relative occurrence of a disease or a condition that causes illness.⏎