How Solving this Medical Mystery Saved Lives | Nat Geo Explores

Not that long ago, we didn't understand why we got sick. There was no internet, and doctors were basically guessing. But then, in the 19th century, a few scientists figured it out: germs. One of the scientists was Louis Pasteur. The milk, already pasteurized, is piped into this filling station. His name might ring a bell because he developed pasteurization, a process that kills off germs in things like milk.

Louis Pasteur was an accomplished French chemist. When he started to investigate the causes of disease, he developed some of the earliest vaccines, including one that virtually saved Europe's chicken industry. His microbiology research also revived France's silk production, and his work on pasteurization saved the French beer and wine industries. Pasteur had become a science rock star.

One of the key moments in persuading the world that germs cause disease occurred on a French farm in 1881. Pasteur got into an argument with a veterinarian who absolutely refused to accept that germs might cause anthrax. Pasteur basically challenged him to a scientific duel. He had fifty sheep, perfectly healthy, set aside. Twenty-five of them were given an anthrax vaccine; the other twenty-five didn't get it.

Not long after, all fifty sheep were injected with a particularly virulent strain. This was huge, especially because press from around the world came to cover the results. The reveal was pretty remarkable: the twenty-five sheep that had passed those experimental vaccines were healthy, while the others were dying, clearly of anthrax. This was splashed on the front pages of newspapers across the world.

Pasteur was a master for PR, but it was necessary for people to fundamentally alter the way they thought about infectious disease to realize that microorganisms were indeed the cause. One really important outcome of the germ revolution was the development of more vaccines. Many infectious diseases can be brought completely under control.

There had been smallpox vaccines that had been available for well over a century, but that was it. As a result of the work of people like Pasteur, you started to see vaccines introduced for anthrax, for cholera, and for typhoid. One of the most important public health innovations was the introduction of what was called pasteurization.

You repeat on a substance like milk, kill off the bacteria, and then it could be sold. It dramatically reduced the number of children who were dying from gastrointestinal illness. In fact, in the 19th century, one out of every four infants passed away before the first birthday due to infectious diseases. After the rise of germ theory and processes like pasteurization, the number of infant mortalities dropped in some places by as much as 50%.

Just over a hundred years since that day on the French sheep farm, pasteurization became law in the United States. In the decades in between, more vaccines were developed, including Louis Pasteur's vaccine for rabies. Medicine had paid ineffective for the entirety of human history and how they were going down the right path.

So, curative medicine came of age, loyalty because doctors knew what actually causes disease.