Curing Cholera, Developing Germ Theory: Revolutionaries in Epidemiology

FROM THE LECTURE SERIES: An Introduction to Infectious Diseases

By Professor Barry C. Fox, M.D., University of Wisconsin

The beginning of the 1800s saw the start of a infectious disease of epic proportions in Europe: Cholera. Presumed to have originated from the Ganges River Delta in India as early as the 1500s, the disease followed world trade routes in the 1800s, killing thousands of people in its wake. Has it been eradicated today?

Image showing importance of clean water.
The cause of cholera was traced to contaminated water. (Image: Riccardo Mayer/Shutterstock)

Effects of Cholera

Cholera victims often died within hours of getting infected. During the six worldwide pandemics caused by cholera, millions died across all continents. However, the world is yet to be rid of cholera. It is still present at low levels in many countries, killing thousands yearly.

Fortunately, today, death from cholera can usually be prevented by early recognition, taking rehydration salts, and massive fluid replacement.

The 1832 Cholera Outbreak in London

In the 1800s, the Miasma Theory of infection was still prevalent, and many believed that cholera was not contagious. In 1832, there was a major outbreak of cholera in London that lasted for 22 years and was referred to as the period of “The Great Stink”.

As in many urban cities of the time, London was over-crowded and lacked good sanitation, which was a perfect breeding ground for diseases. In August of 1854, a major outbreak of cholera struck the Soho district of London. Dr. John Snow, an English physician, did not believe in the Miasma Theory and hypothesized the disease was being spread through contaminated drinking water.

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Cholera through Contaminated Water

Without an efficient sewage system, all waste was being dumped into the Thames River, the source of London’s drinking water. Dr. Snow showed that two water companies were taking water from sewage-polluted sections of the Thames and delivered the water to homes that had higher incidences of cholera.

He went door-to-door asking questions, and finally hypothesized that the source of the disease might be the public water pump on Broad Street in Soho. As an emerging epidemiologist, Dr. Snow had discerned that the death rates were proportional to the proximity to that particular pump. When he managed to convince the city council to remove the pump handle, the rate of cholera improved dramatically.

Dr. John Snow’s use of statistical methods and his case study can be regarded as the founding event in the world of epidemiology.

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Robert Koch and the Germ Theory of Disease

Image showing an illustration of Robert Koch.
Robert Koch was responsible for identifying the specific cholera germ. (Image: Morphart Creation/Shutterstock)

In 1883, Robert Koch, a bacteriologist in London, finally identified the specific cholera germ—cholera bacillus.

One of the most influential bacteriologists in history, Koch also proved that microorganisms caused anthrax and tuberculosis. His work was important in proving the germ theory of disease, and that diseases were contagious.

Development of the Germ Theory

With the help of Robert Koch, Edward Jenner and later Louis Pasteur, germ theory began to be refined in the mid-19th century. It stated that specific microorganisms are the cause of specific diseases.

This theory radically changed the practice of medicine. Scientific proof of this theory was provided by the laboratory research of Louis Pasteur and Robert Koch. Together, their work drove the research that helped identify dangerous germs and develop life-saving treatments.

This is a transcript from the video series An Introduction to Infectious Diseases. Watch it now on The Great Courses Plus.

Louis Pasteur and Modern Medicine

An old photograph of Louis Pasteur.
Louis Pasteur’s contributed greatly to progress in the field of scientific discovery and invention. (Image: Everett Collection/Shutterstock)

Some of Louis Pasteur’s first work was with winegrowers in France—trying to ascertain the cause for grape blight.

Pasteur demonstrated that wine diseases were caused by microorganisms that can be killed by heating the wine to 55 degrees Centigrade for several minutes. Hence the process was named “pasteurization”.

He also discovered that beer and milk spoiled because of the rapid multiplication of microbes in these liquids, and this could be prevented through pasteurization.

Pasteur Discovers Vaccines

For his work, Pasteur was subsequently granted a U.S. patent “for improvement in brewing beer and ale pasteurization”. In 1885, Pasteur discovered vaccines for chicken cholera, anthrax, and even the first rabies virus vaccine.

Since rabies is one of the most uniformly fatal infectious diseases, the rabies vaccine has significant implications. Rabies was too small to be seen under any microscope at the time, leading to the concept of smaller organisms, which is known as viruses. Louis Pasteur created the Pasteur Institute that encouraged the freedom of creative imagination and rigorous scientific experimentation.

The Chamberland-Pasteur Filter

Pasteur worked together with another scientist, Charles Chamberland, to invent a device that would enhance the discovery of viruses. In 1884, the Chamberland-Pasteur filter was developed, which completely removed all bacteria from a liquid suspension.

By doing this, scientists were able to prove that an unknown infectious substance remained in the liquid and passed through the smallest caliper filters. Hence, they speculated the existence of viruses even before they were seen.

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The Electron Microscope

The invention of the electron microscope in the 1930s enabled scientists to finally see viruses, which are about 100 times smaller than bacteria. For this microscope to work, electrons, which are subatomic particles, are accelerated in a vacuum space at short wavelengths.

These electrons are directed to a target to form an image on an electron-sensitive photographic plate. Magnification can occur up to 1 million times the original object. Unfortunately, no living specimen can survive the high vacuum pressure and bombardment of electrons, so the microscope cannot show the organism’s dynamic life process.

Many of the worst diseases were found to be caused by specific bacterial or viral pathogens. Vaccines were produced against some of the organisms and by the 1950s, antibiotics would begin to cure others. But in the 1960s and 1970s, scientists were potentially becoming overly optimistic about the future conquest of infectious diseases.

Common Questions about Revolutionaries in Epidemiology

Q: According to Dr. John Snow, how did cholera spread?

Dr. John Snow hypothesized that cholera was being spread through contaminated drinking water.

Q: What did Robert Koch identify in 1883?

In 1883, Robert Koch, a bacteriologist in London, identified the specific cholera germ—cholera bacillus.

Q: How did the term “pasteurization” originate?

The term “pasteurization” originated when Louis Pasteur demonstrated that wine diseases are caused by microorganisms that can be killed by heating the wine to 55 degrees Centigrade for several minutes.

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