Understanding Contagion and Germ Theory: Science and Cleanliness Shaming

This article is an attempt by an independent science blogger fed up with corruption and corporate hijacking of science, to create a clear, respectful, and fact-based language appropriate for a 6th-grade reading level about germs, a topic that causes many disagreements. The goal is to present an honest view that acknowledges important nuances about contagion.

Germ theory is the scientific idea that invisible germs (microbes) cause certain diseases, when conditions are right. Learning about contagion and germ theory helps us understand how some kinds of diseases spread and how to protect ourselves and others, but we must also understand that there are many helpful microbes, and the balance of germs we meet matters.

Understanding Germs Without Feeling “Dirty” or Rejected

Most viruses and bacteria are helpful or harmless, forming a complex community inside and on our bodies called the microbiome. These microbes support digestion, immune function, and protect against harmful germs. Only a small fraction cause contagious diseases. Germs are simply part of the natural world, like pollen or dust.

However, some people strongly resist germ theory because of emotional experiences and deeply held beliefs. For example, if as children they were shamed or rejected for being “dirty,” they may react with fear, anger, or denial when hearing about germs and disease spread. This resistance can also stem from a desire for certainty and control—believing that health depends solely on personal choices and cleanliness feels safer than accepting vulnerability to invisible germs.

This kind of thinking—often black-and-white or rigid—is common in some religious or cultural views that see illness as punishment for moral failings or impurity. Such beliefs can cause stigma, shame, and social isolation of sick individuals, worsening emotional pain and mistrust of medical science.

Science shows that germs do spread between people and cause many illnesses, but this is not about being “dirty” or “bad.” It’s about how germs interact with our bodies and immune systems. Most microbes we share with others are beneficial or neutral, helping keep us healthy.

Understanding this helps separate the science of contagion from the emotional pain caused by stigma or past rejection. Feeling ashamed or scared about germs is natural given these experiences, but learning the facts can empower us to protect ourselves and others with kindness and respect—without blame or judgment.

Effective communication about germs requires empathy first—acknowledging fears and feelings—before sharing scientific facts. Recognizing the emotional and cultural roots of germ denial helps build trust and encourages healthier attitudes toward disease prevention.

How Do People Catch Illnesses?

Catching an illness depends on two main things:

Exposure to germs: You have to come into contact with the germs that cause the illness. This can happen through touching, breathing in droplets, or being near someone who is sick.

Your immune system health: Your body’s defense system fights off germs. If your immune system is strong, you might not get sick even if exposed. But if it’s weak, you are more likely to catch the illness.

Environmental pollution, like smoke or chemicals, can make your immune system weaker or irritate your body, making it easier for germs to cause infection. But pollution itself does not cause contagious diseases — it only helps germs take hold more easily.

Masks and How They Work

Masks can help reduce the spread of germs, but not all masks work the same way. Some cloth masks may not stop tiny virus particles effectively and, in some cases, might even spread droplets further by breaking them into smaller particles that float in the air longer. Masks that fit well and are designed to filter small particles — like N95 or similar respirators — are better at stopping germs from spreading.

Also, wearing a mask for a long time can sometimes make people feel uncomfortable or breathe in more carbon dioxide they exhale. Scientists study these effects carefully because breathing in too much carbon dioxide over time can affect health. It’s important to use masks properly and take breaks if needed, especially for children or people with breathing difficulties.

Vaccines: What You Should Know and What You Can Trust

Good evidence from decades of experiments shows that, in some cases, giving the body small amounts of certain substances can help protect people from some diseases by training the immune system to recognize and fight germs. However, it’s very important that all vaccines are tested carefully for safety and effectiveness over many years before they are recommended for everyone.

People have the right to choose whether to get a vaccine, especially if the vaccine has not been fully tested or if there are known risks like serious side effects. Trust in vaccines depends on honest sharing of all scientific data, including how studies were done and who funded them. When this information is clear and complete, people can make informed decisions about their health.

Why Some People Question Contagion — And What Science Shows

Some people say that diseases are caused mainly by pollution or other factors, not by germs spreading between people. It’s true that environment and personal health affect whether someone gets sick. But many scientific experiments have shown that some germs do spread from person to person, causing contagious diseases.

For example:

Scientists have infected some animals with a virus and then placed healthy animals nearby. The healthy animals got sick, proving the disease spread through contact or air.
Studies tracking how illnesses spread in groups of people show that close contact increases the chance of catching diseases.
Experiments have shown that tiny particles in the air can carry viruses that infect others.

These studies are carefully done to make sure germs are the cause of the illness spreading.

Remember, however, that there are also good microbes we constantly share and exchange by intereacting with others. Many of these make us healthier. When a rare bad germ going around, you have the option to avoid getting sick by cleaning surfaces, washing hands, and, perhaps wearing a mask in public spaces.

How Do Experiments Rule Out Environmental Pollutants as the Cause of Illness Spread?

Sometimes, the symptoms caused by pollution and contagious diseases can look alike. Pollution usually harms animals by hurting their lungs, skin, or other parts of the body, causing problems like trouble breathing or skin irritation. Contagious diseases often cause fever, coughing, sneezing, and can spread from one animal to another. Because some symptoms, like coughing or breathing problems, can happen with both pollution and infections, scientists use tests and other clues to tell them apart. Knowing the difference helps keep animals and people healthy.

Scientists use experiments designed carefully to separate the effects of germs from pollution. Here’s how they do it, explained in a way that is easy to understand:

Proving Germs Must Be Alive to Cause Infection: The Role of Autoclaving
An autoclave is a high pressure steam oven. Scientists use a process called autoclaving to kill germs by applying high heat and pressure. More precisely, an autoclave is a sealed chamber that applies steam under pressure (usually around 15 psi above atmospheric pressure) at high temperatures (typically 121°C or 250°F) for a set amount of time. This combination of heat and pressure kills bacteria, viruses, spores, and other microorganisms, making items sterile. When germs are autoclaved, they are completely inactivated and cannot cause disease. Experiments show that animals or surfaces exposed to autoclaved (dead) germs do not get sick. This proves that germs must be alive and active to cause infections. It also helps scientists separate the effects of germs from other factors like pollution, because pollution particles are not alive and cannot cause infection either. This type of sterilization testing is a key part of understanding how contagious diseases really spread.
Keeping pollution the same, changing germs: Scientists study groups of animals or people in places where pollution doesn’t change much. Then, they expose some to germs and others not. If only the ones exposed to germs get sick, it shows germs cause the disease, not pollution.
Combining Pollution and Germs: Pollution can harm bodies, such as damaging organs or weakening their immune systems. Experiments show that when animals are exposed to both pollution and germs, they tend to get sicker than when exposed to germs alone. This means pollution can make it harder for animals to fight infections, but pollution by itself does not cause contagious illnesses.
Using clean air and filtered environments: In some experiments, germs are put into clean air or special containers that keep pollution out. When germs spread illness in these clean conditions, it proves pollution is not needed for the disease to spread.
Watching how germs move: Scientists track who gets contagious diseases and when and where. They also track tiny droplets or particles that carry germs when someone coughs or sneezes. These droplets can float in the air and infect others. When animals are exposed to pollution alone, without the germs, they do not develop contagious diseases caused by germs.
Testing surfaces: Germs can live (or remain contagious) on surfaces for some time. Experiments show that cleaning those surfaces lowers infection rates.
Looking at immune system effects separately: Scientists know pollution can affect the immune system, sometimes making it harder to fight germs. Experiments show pollution alone can make people sick, but it doesn’t cause the same symptoms as contagious diseases. Pollution makes it easier for germs to infect someone.

By doing these kinds of experiments, scientists have shown that germs are the main cause of contagious diseases, while pollution is a separate factor that can influence how sick someone gets but does not cause the disease to spread on its own.

These kinds of careful testing are why doctors and scientists trust germ theory to explain how many diseases spread and how to stop them.

How Pollution Affects the Immune System and Disease Risk

Scientific studies show that air pollution can change how the immune system works. When people breathe in polluted air, tiny particles and gases can cause inflammation—this means the body’s defense system becomes active in a way that can sometimes be harmful instead of helpful.

Pollution–such as chemicals or other irritants in air, water, or food–can:

Increase the production of substances called cytokines that cause inflammation in the lungs.
Change how immune cells behave, sometimes making them less able to fight germs properly.
Weaken important immune functions, like the ability of certain cells to “eat” and remove harmful germs.
Make it harder for the body to control viral infections by reducing antiviral responses.

Because of these effects, people exposed to high levels of pollution may have a higher chance of getting infections like colds, flu, or other respiratory illnesses. Pollution does not directly cause contagious diseases, but it can make the body less able to defend itself against germs that cause those diseases.

Ecology: The Percentage or Number of Germs Matters

If you eat a little bit of ice cream or candy, your body will use the sugar for energy and it probably won’t be bad for you, but if you eat too much, the sweets will make you sick. Similarly, one virus or one bacteria is not going to make any animal with a healthy immune system sick. It usually takes a certain number of germs—called the “infectious dose”—to overcome the body’s defenses and cause illness. The more germs you are exposed to at once, the more likely you are to get sick. That’s why being close to someone who is coughing or sneezing a lot increases the chance of catching their illness, because you breathe in more germs. Your immune system works hard to fight off small amounts, but when the number of germs is too high, it can get overwhelmed and illness can develop.

If you put a bunch of different colored marbles in a small space and look at it from a distance, you will see the overall color. If green marbles are germs, the marble collection will only start to look green from a distance if you have enough of them in the collection. This is a nice simple way to visualize how infection works. You don’t get sick (green) until the number of green marbles is more than the collection can stand.

Why Science and Trust Matter

Science works best when all data and methods are shared openly, so other scientists can check and repeat experiments. This openness builds trust and helps us find the best ways to stay healthy.

Unfortunately, people need money and even big important organizations sometimes lie and cheat to make this money. The system where industry pays for science can get out of balance. It is not usually the case, but a few things have been called “safe and effective” which later where shown to be unsafe or ineffective. Sometimes, people or organizations may use science in ways that are not fully honest or clear. This can cause confusion and make people distrust real science. Thankfully, real trustworthy science does exist. Science does correct itself over time. It’s important to ask questions, look at the evidence carefully, and to remember that science done right is a process that is constantly improving.

Article Summary

Catching contagious diseases depends on exposure to germs and the strength of your immune system. Environmental factors like pollution can influence your risk but do not replace the role of germs in spreading illness. Masks can help protect us, but only certain types are effective. Vaccines can keep us safe, but they must be proven safe and effective through careful, transparent studies—simply claiming something is “safe and effective” isn’t enough. Science works best when it is open, honest, and based on solid evidence.

At the same time, it’s important to remember that learning about germs is not about judging anyone or making people feel “dirty.” Everyone encounters germs every day, and getting sick is not a sign of being “bad” or “unclean.” Understanding how germs spread helps us protect ourselves and others with kindness and respect, without shame or fear. This way, we can care for our health and each other with both knowledge and compassion.

If you feel sick, it’s reasonable to avoid contact with others until you recover. If you are healthy, spending time with other healthy people can be beneficial, as sharing harmless microbes helps strengthen our immune systems.