GERM THEORY: THE FOUNDATION OF MODERN MEDICINE 

| March 29, 2024

Medical science has come a long way in the past few centuries. In earlier times, it was believed that an imbalance in body fluids or “humours” caused diseases and that extracting blood from patients could cure them [1]. Later, the miasma theory among others, suggested that diseases like cholera were caused by bad air from rotting organic matter [2]. However, the discovery of the microscope by scientists, one of the most notable being Antonie van Leeuwenhoek ushered in a new era of medical understanding [3]. The germ theory of disease was introduced in the 19th century and proposed that microorganisms spread illnesses. This theory led to the identification of diseases caused by microbes and finding ways to prevent them through immunization, sanitation, and better living conditions. By the mid-1960s, experts believed that infectious diseases were almost eliminated, so researchers could focus on chronic medical conditions like heart disease and cancer [4].

Robert Koch a German physician, microbiologist, and one of the proponents of the germ theory conducted experiments with anthrax in the late 1800s to establish that a specific germ could cause a particular disease. He found rod-shaped bacteria in the blood of cows that had died of anthrax and suspected that they caused the disease. When he infected mice with blood from the anthrax-stricken cows, the mice also developed anthrax. Koch established four criteria, known as Koch's Postulates, to determine whether a germ causes a specific disease. Even today, it is impossible to prove that a specific germ causes a disease without the use of laboratory animals [5].

Scientists today recognize that microbes and their hosts, including humans, depend on each other for survival. While disease-causing microorganisms receive more attention, most microorganisms do not cause illness. Many of them protect us by helping our bodies function properly and competing with harmful organisms in an ongoing battle for habitable space in and on our bodies. While the few microbes that cause illness receive a lot of attention, it's important to note that new infectious diseases continue to emerge, and old ones are appearing in new locations around the world. According to the World Health Organization (WHO), infectious organisms are responsible for about a quarter of all deaths worldwide, many of which are children [5].