This document discusses health, illnesses, and how diseases are transmitted and prevented. It defines health as a state of physical, mental, and social well-being. Illnesses are caused by problems in the body's organs. Infectious diseases are caused by microorganisms like bacteria, viruses, protozoans and fungi, and can be transmitted through personal contact, droplets, contaminated objects, animals, food, or water. Non-infectious diseases are not caused by microorganisms. To prevent diseases, people should maintain a healthy lifestyle with hand washing, vaccinations, dental hygiene, and more.