The Germ Theory

The Germ Theory of disease posits that many illnesses are caused by microorganisms, such as bacteria, viruses, and fungi. These tiny organisms can invade the body, multiply, and disrupt normal bodily functions, leading to sickness. This theory revolutionized medicine in the 19th century by explaining how infections spread and how diseases could be prevented through hygiene, vaccination, and sanitation. It shifted the understanding of disease away from causes like "bad air" or imbalances in bodily fluids, providing a scientific basis for treatments and public health measures that protect and improve human health.