What is the proof that germs cause diseases? Is this just a “theory” without any evidence? I heard this claim on a YouTube video recently and listened curiously for a while to see if they were making any sense, or if it was a joke. There are occasionally big paradigm shifts. Once in a while things we thought were true get overturned. Einstein’s theory of relativity was one example.
After watching the video, however, I was not convinced. The arguments were flawed. One said that for a germ to be the cause of illness, it must always cause illness. This is obviously not true. The same germs do not cause disease in everyone for many different reasons: some have developed natural immunity via the human adaptive immune system, some are on antibiotics, some take supplements that destroy the germs in the gut or elsewhere before they can multiply. Other factors include the virulence of the bacterial strain, and the site of infection.
The people speaking did not seem to understand that a single bacteria is not the problem. Bacteria are very small and by the time they make you sick, there are large numbers of them in your system. This is somewhat understandable as the precise minimum number of any bacteria required for illness to manifest is not clearly defined in the literature. Observational studies suggest that the infectious dose for certain pathogens may range from around 100 to 400 plaque-forming units (PFU) on average. Additionally, the infectious dose for norovirus, a highly contagious pathogen, can be as small as 18 individual viruses. {Source}
If you have enough of certain kinds, you get sick. If you have just a few even very bad bacteria, yeast, or whatever, you generally don’t ever notice because your body is constantly fighting invaders, repairing damage and flushing germs out of your system.
It bears repeating that we are not all the same. Not everyone has the same allergies, for example, but this does not mean that allergies are not caused by allergens. It is true that some strep bacteria can be found in people who do not have strep throat. This only shows, again, that there is a certain threshold under which that person’s immune system can keep bacteria at bay. There are also people who have sore throats for other reasons. This argument does not show that streptococcus bacteria is not the cause of strep throat. Streptococcus bacteria, specifically Streptococcus pyogenes, also known as group A Streptococcus (GAS), is a well-established cause of strep throat.
Another complaint by the people in the video was that scientists at first called things bacteria then later called them viruses, therefore, the whole thing is a hoax. That does not follow logically. Both bacteria and viruses are found in the body at the same time. A secondary bacterial infection can be caused by a viral infection. A viral infection damages some cells, after which bacteria can invade the weakened cells. This is why antibiotics are sometimes given when there is a primary virus caused disease. Antibiotics are not given if the only problem is a virus because most antibiotics do not harm viruses (although some do).
Some germs do cause some diseases. Some things count as evidence, and others don’t. Authority is not proof. This is very difficult concept for many people to accept, because they do not like the consequences of that truth: you have to personally continually learn and analyze, and hey, that’s hard work.
With that tout of the way, lets look at the evidence for the germ theory of diseases, step by step.
Evidence for the Germ Theory of Disease
1) Distinct Germ Types: There are differences in types of germs. We know this from microscope observations, genetic sequencing, and from the results they have when introduced into animals. We have categorized many microbes. (See this.)
2) Correlation: Certain germs are always found in diseased tissues in a direct relationship. Millions of laboratory tests have been done all around the world for decades that consistently show that people and animals with certain diseases have certain common microbes. In a herpes cold sore, we find herpes virus. In anthrax disease, we find the anthrax virus. In cervical cancer, we find HPV, another virus. In people with the flu, we find influenza virus. In people with colds, we find the cold virus. In people with strep throat symptoms, we find strep bacteria. The list is long, but you have heard of man, no doubt. Anthrax is caused by Bacillus anthracis, Bubonic plague is caused by Yersinia pestis, chickenpox is caused by Varicella zoster virus (VZV), chlamydia is caused by Chlamydia trachomatis, gonorrhea is caused by Neisseria gonorrhoeae, malaria is caused by Plasmodium species, measles is caused by Measles virus, mumps is caused by Mumps virus, rabies is caused by Rabies virus, and so on.
3) Causation Confirmed: Countless experiments show cause and effect. To study diseases, they are purposefully given to experimental animals. This would not work if scientists could not isolate the cause of each disease, the germs, and then cause the disease in healthy animals by giving them the germs. You don’t cause chicken pox by giving measles virus to an animal. That doesn’t happen. You don’t give an animal the plague virus and cause it to have rabies. There is a one to one relationship demonstrated over and over, repeatedly and reliably. None of the studies with animals and these diseases would work if this was not true. But they do work. This has been shown time and time again with countless experiments when studying these diseases over the last 140 years.
4) Natural Causation: Outside of animals, we can observe the germs causing diseases. Germs infect and kill cells in cultures and this is observed under microscopes. We see them busting into cells and breaking the cells. We see them erupting from the dead cells and then going and infecting other healthy cells. This is not due to “something else” with the germs just eating the dead cells, because the exact same bunch of cells not given the germs do not break open and die. They keep reproducing other healthy cells. Scientists did not forget to check this.
Scientists Who Did Foundational Experiments
In the video I watched which caused me to write this, the people were asking where they foundational papers were which show diseases are caused by germs.
1. Robert Koch’s experiments with anthrax in the final decades of the 19th century, where he conclusively established that a particular germ could cause a specific disease, are pivotal in demonstrating the germ theory of disease[1].
2. Louis Pasteur’s work on fermentation and the role of living organisms in causing disease laid the foundation for the modern germ theory of disease[5].
3. Koch’s Postulates, which prove that specific germs cause specific diseases and that disease germs transmit disease from one body to another, are fundamental to the germ theory of disease[3].
4. Joseph Lister, a physiologist and surgeon, is known for inventing antiseptic surgical techniques, which significantly reduced the infection mortality rate[3]
5. Florence Nightingale and Rudolf Virchow were important proponents of hygiene and sanitation, which are integral to the understanding of the germ theory of disease[3]
6. Girolamo Fracastoro: In the 16th century, Fracastoro scientifically explored and understood the nature of germs, infection, contagion, and disease transmission[6].
7. Athanasius Kircher: In the 17th century, Kircher made significant contributions to early germ theories[3].
Additionally, the disproval of spontaneous generation was an important early development in the germ theory, laying the groundwork for future advancements in understanding the role of microorganisms in causing disease. [3]
What Are Germs?
Germs include mold, bacteria and viruses. The sizes of germs vary, with bacteria, viruses, fungi, and protozoa being of different dimensions. Here are the typical sizes of these microorganisms:
Bacteria: Bacterial cells are typically about 1 µm in size[11]. They are single-celled organisms that can be spherical (coccus), rodlike (bacillus), or curved (vibrio, spirillum, or spirochete)[10].
Viruses: Viruses are even smaller than bacteria, ranging in size from about 20 to 400 nanometers in diameter[10]. They are not considered full cells and consist of genetic material (DNA or RNA) packaged inside a protein coating[9].
Fungi: Fungi are multicellular, plant-like organisms. The size of fungi can vary, but they are generally larger than bacteria and viruses[9].
Protozoa: Protozoa are one-celled organisms that are bigger than bacteria and contain a nucleus and other cell structures, making them more similar to plant and animal cells[9].
These sizes provide an understanding of the relative dimensions of different types of germs.
Prove Germ Theory to Yourself: Fungi Experiment
Fungi experiment: Spray a counter top with a mist of 2% hydrogen peroxide to sterilize an area. Choose a place with little air flow. Take some real cheese (not plastic American cheese, which has preservatives) and slice it in three equal sizes. Wrap one third immediately and tightly in Saran wrap. Next cover one with a few layers of cheese cloth all around, and leave the third other uncovered. Quickly check and then recover them at 8, 24 and 48 hours and document any mold. You will notice mold forms on the unprotected cheese most. Why is this? Does mold form when the cheese cloth lets in air but blocks particles like mold spores? As to fungus causing illness, if you’ve ever had athlete’s foot, an incredibly itchy fungus which you cured with an anti-fungal ointment, you will no longer doubt. If you want to try antibiotics instead of an anti-fungal, go for it, itchy foot person.
Prove Germ Theory to Yourself: Virus Experiment
To prove the germ theory, with regard to viruses, you could use the tobacco mosaic virus (TMV). A simple experiment can be conducted to demonstrate the infectious nature of the virus. The experiment can involve infecting a healthy tobacco plant with the TMV and observing the development of characteristic mosaic patterns on the leaves. This can be done by obtaining a sample of TMV-infected plant material, grinding it in a buffer solution, filtering it with a Chamberland filter to remove all larger bacteria, and then rubbing the filtered extract with virus onto the leaves of a healthy tobacco plant. Over time, the appearance of mosaic patterns on the leaves of the infected plant will show as evidence of the infectious nature of the virus, supporting the principles of germ theory. [8] By conducting an experiment like this with an understanding of the historical significance of TMV, you can effectively demonstrate and validate germ theory in relation to viral infections.
Prove Germ Theory to Yourself: Bacteria Experiment
While this is not recommended, you could, if you are still suffering from severe doubt in germ theory, infect yourself with a bacteria to prove that a specific bacteria causes a specific disease. You should not do it, but you could. One of the simplest and most famous experiments that demonstrated the link between bacteria and disease was conducted by Barry Marshall and Robin Warren. In 1981, they discovered that a bacterium called Helicobacter pylori was associated with the development of gastric ulcers. To prove this, Marshall ingested a solution containing the bacterium, which led to the development of acute gastric inflammation and early ulcer formation. This experiment provided compelling evidence that the bacterium was implicated in the common disease of peptic ulcer[12]. We also know from many studies that the bacteria Streptococcus mutans causes dental cavities.[13] Clinical studies have identified several molecular mechanisms by which Streptococcus mutans efficiently enhances biofilm biomass, promoting the demineralization of tooth tissues and contributing to the establishment of cariogenic microbiota. Translation: a specific group of bacteria has been shown by research to promoting a certain range of microorganisms which initiate removal of minerals that make up teeth resulting in holes or cavities[14].
Summary
There is no other credible explanation than germ theory being correct to explain 140 years of research followed by the work of Louis Pasteur published on April 29th, 1878. If you want the earliest foundations, you can read his paper. [7] The reason it is still around today, over 145 years later, is that it was showed to be correct (and very useful) by many many other researchers who tested it on their own. To overturn this, you would have to overturn more than Louis Pasteur, you would have to explain why a particular germ always gives a particular disease in tests all around the world for well over a century. Countless experiments conducted in various fields of biology, medicine, and microbiology that have consistently provided evidence for the existence and role of microorganisms in disease transmission.
Citations:
[1] https://www.ncbi.nlm.nih.gov/books/NBK24649/
[2] https://www.sciencedirect.com/topics/immunology-and-microbiology/germ-theory-of-disease
[3] https://curiosity.lib.harvard.edu/contagion/feature/germ-theory
[4] https://en.wikipedia.org/wiki/Germ_theory_of_disease
[5] https://biotech.law.lsu.edu/cphl/history/articles/pasteur.htm
[6] https://kinnu.xyz/kinnuverse/history/medical-breakthroughs/germ-theory/
[7] https://sourcebooks.fordham.edu/mod/1878pasteur-germ.asp
[8] https://www.smithsonianmag.com/science-nature/what-are-viruses-history-tobacco-mosaic-disease-180974480/
[9] https://kidshealth.org/en/teens/care-about-germs.html
[10] https://www.ncbi.nlm.nih.gov/books/NBK209710/
[11] https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(OpenStax)
[12] https://www.sciencefocus.com/the-human-body/the-experiment-that-proved-bacteria-caused-disease
[13] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC373181/
[14] https://link.springer.com/article/10.1007/s40496-013-0008-1