We often hear in the news that a new virus is causing a new disease. Just like we heard during the coronavirus pandemic, scientists discovered that a coronavirus was the cause of the disease called SARS. But have you ever wondered how these scientists can say so precisely, so confidently, that this virus is the cause of this disease? Is it just a guess? Or is there some accepted method for it? We are talking about that secret today.
Scientific Secret: Robert Koch's Postulates
This is not really a guess. There is a very specific scientific method that scientists use to prove that a specific germ is the cause of a disease. It is like a police investigation, a step-by-step process to catch a suspect. This method was first introduced to the world as far back as 1890 by a German doctor and scientist named
Robert Koch . We call these laws that he proposed
"Koch's Postulates." Simply put, this is the "book of four laws" that scientists use to prove that a germ is the "culprit." Let's see what these four laws are.
| Koch's Postulate | What does this mean? (Simply) |
|---|
| First rule | Every patient with the disease in question must have this suspicious germ in their body. Likewise, healthy people without the disease cannot have this germ in their body. |
| Second law | It should be possible to grow the germ in a lab culture, in a special medium, from tissue or other samples (for example, phlegm, blood, stool) taken from a sick person. |
| Third law | When that pure germ, grown in a laboratory, is introduced into the body of a healthy, susceptible animal (or person), it should develop the same original disease. |
| Fourth law | It should be possible to isolate and cultivate the same original germ again from a sample taken from the second newly infected person or animal. |
But a healthy person can't spread the disease, right?
Now you're probably having a big problem. Look at that third law. Isn't it morally wrong to infect a healthy person with a disease? It's impossible. So how do scientists fulfill this law?
Yes, that story is completely true. No one intentionally infects people with a disease and conducts experiments for any reason. That's a big mistake. That's why scientists use other methods to prove these third and fourth laws.
The scientific methods used for it
1.
Epidemiology: This is the main method. Simply put, epidemiology is the study of the patterns of disease spread among a population. Like a detective, scientists look for:
- Who got the disease?
- Where were they?
- Who did they hang out with?
- What are the common links between people who have contracted the disease?
- This information is then compared with information from a healthy group of people who have not developed the disease.
Imagine, if everyone who got SARS was exposed to the virus and the unexposed people did not get sick, that would be strong evidence that the cause of the disease was exposure to the virus. In this way, the principle of the Third Law can be proven without infecting a person. 2.
Animal Models: The other method is animal testing. Animals that show symptoms similar to humans (e.g., mice, monkeys) are injected with a virus grown in the laboratory. If that animal develops a disease similar to that of humans, that confirms the Third Law. If the virus can then be isolated from that animal again, then the Fourth Law is also true.
This is how the SARS virus was identified!
Now let's see how these rules were applied to the SARS epidemic.
- First and Second Laws: Scientists isolated the coronavirus from several patients with SARS symptoms. And they successfully grew the virus in the lab. So both first laws are fulfilled.
- The Third and Fourth Laws: This is where epidemiology comes in. The tests clearly showed that the disease was widespread among those who had been exposed to the virus, and that it was not present among those who had not been exposed. In addition, some people who had been exposed unexpectedly (e.g., health care workers who had cared for patients) also became ill later, and the original virus could be isolated from them. This confirmed the principles of the Third and Fourth Laws. This was also further confirmed by animal studies.
So now you know, this is not just a guess. This is a very logical, systematic, centuries-old, and very reliable scientific process.
Take-Home Message
- Scientists determine that a disease is caused by a specific virus or bacteria, not by guesswork, but by following a scientific method called "Koch's Postulates."
- This method involves four main steps: identifying the germ from patients, growing it in the laboratory, showing that it causes the disease, and isolating the same germ again.
- Because it is unethical to intentionally infect humans with diseases, scientists confirm the principles of these laws through methods such as epidemiology and animal testing.
- So, from now on, when you hear that a certain disease is caused by a virus, remember the rigorous scientific process behind that statement.
- If you have any medical condition or have any doubts about it, always consult your doctor for advice .
Virus, diagnosis, Koch's laws, scientific method, epidemiology, SARS, coronavirus
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