Germ Theory: A Medical Masterpiece


Modern medicine has contributed to many revolutions that changed the world. Over time, global life expectancy has risen, and quality of life has improved significantly. One advance that enabled this is the germ theory of disease, which states that pathogens are causes of illness. Understanding the cause of an illness is crucial for developing preventative measures and treatments to diseases.

The work of obstetrician Ignaz Semmelweis is vital to the history of this theory. In 1847, he noticed that many mothers died from puerperal fever but only when doctors and medical students treated them. As they were involved in autopsies and the fever is highly contagious, Semmelweis thought that there was a connection between all these factors. He made sure the doctors wash their hands with chlorinated lime water, and the mortality rates plunged to 2.2% in a year! 

But the Royal Society ignored his findings. Fortunately, scientists such as Louis Pasteur were intrigued by his idea. His experiments on fermentation in anaerobic conditions disproved the currently-accepted miasma theory, which stated that diseases were caused by “bad air”. He also pointed out that there are three different approaches to get rid of microorganisms: filtration, high temperatures or the use of certain chemical compounds. 

Surgeon Joseph Lister read Pasteur’s research and was intrigued. Surgery at the time was a considerable risk to the patient. Due to surgeons believing in the “miasma” theory, there was no sterilisation of equipment or even washing of hands and gowns. This promoted the spread of gangrene, a disease that results in tissue death due to a loss of blood supply. Though there are a few causes for gangrene, the main culprit, after surgery, was a bacterial infection, and this was responsible for many postoperative deaths. Lister thought that Pasteur’s results could end this problem. Filtration and exposure to heat weren’t sensible options. Hence, Lister thought a chemical that could be used to get rid of the infection. He decided to use carbolic acid, spraying it on the surgical equipment and incisions on the body. Remarkably, the rates of disease fell significantly, and the postoperative mortality rates plummeted. 

Once the scientific community accepted the germ theory, more steps were taken to make surgery as safe as possible: the introduction of scrubs and gloves, autoclaving equipment and development of better disinfectants. Furthermore, the scope of surgery expanded exponentially, being able to operate in many different areas in the body. The rigorous process of sanitation has developed in other areas, such as water treatment, food preparation and personal hygiene. Thus, many more lives were saved by merely understanding that germs can cause disease.

Germ theory had impacts elsewhere in medicine. Shortly after Pasteur published his findings, Robert Koch, a German scientist, took inspiration and conducted his research. First, he proposed the Four Postulates, which scientifically prove that a particular microorganism causes a specific disease. Next, he and his assistant Julius Petri made observations of bacteria a lot simpler, through the development of agar jelly (a growth medium for bacteria), the famous Petri dish and several stains. Koch himself used these techniques to identify the bacteria causing tuberculosis and cholera, and other researchers used the same methods to discover the bacteria causing typhus, tetanus and the plague. Over time, the older methods were improved, and newer techniques were developed. As a result, scientists could discover many different types of pathogens and the diseases they caused.

By knowing what causes specific diseases, treatments could be developed to prevent or reduce symptoms. Many antibiotics were discovered, as well as synthesised, which increased the survival rates from many bacterial infections. Antiviral drugs were developed to combat viral infections. Also, many vaccines were invented, and countless lives were saved from diseases such as polio, diphtheria, tetanus and many more. On another note, there is a lot of ongoing research to treat more diseases. One exciting research topic concerns phage therapy – using viruses that infect bacteria. In cases when antibiotics fail, this could be the last resort to save a dying patient from a bacterial infection.

Overall, germ theory has revolutionised medicine and improved the global quality of life because it identified the cause of diseases, allowing for many solutions to be developed.


  1. n.d. Robert Koch | Science Museum Group Collection. [online] Available at: <> [Accessed 7 May 2020].
  2. Burns, H., 2007. Germ theory: invisible killers revealed. BMJ, 334(suppl_1), pp.s11-s11.
  3. Encyclopedia Britannica. n.d. Joseph Lister | British Surgeon And Medical Scientist. [online] Available at: <> [Accessed 7 May 2020].
  4. Lin, D., Koskella, B. and Lin, H., 2017. Phage therapy: An alternative to antibiotics in the age of multi-drug resistance. World Journal of Gastrointestinal Pharmacology and Therapeutics, 8(3), p.162.


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