This document outlines basic principles for preventing infectious diseases, including measures targeting the source of infection, transmission mechanisms, and population susceptibility. It discusses eliminating or decontaminating sources through measures like exterminating infected animals or isolating sick individuals. It covers stopping transmission by improving sanitation, ventilation, and health education. It also addresses stimulating population immunity through vaccines, immunization programs, and developing herd immunity. The three approaches work best together to effectively fight infectious diseases according to their specific characteristics and the situation.