Curing cholera, developing the theory of germs: revolutionaries in epidemiology
Through Professor Barry C. Fox, MD, University of Wisconsin
The early 1800s saw the onset of an infectious disease of epic proportions in Europe: cholera. Believed to have originated in India’s Ganges Delta as early as the 1500s, the disease followed global trade routes into the 1800s, killing thousands in its wake. Has it been eradicated today?
Effects of cholera
Cholera victims often died within hours of being infected. During the six global pandemics caused by cholera, millions of people have died on all continents. However, the world is not yet free from cholera. It is still present at low levels in many countries, killing thousands of people each year.
Fortunately, today, death from cholera can usually be prevented by early detection, taking rehydration salts, and massive fluid replacement.
The 1832 cholera epidemic in London
In the 1800s, the theory of miasma infection was still prevalent, and many believed that cholera was not contagious. In 1832, there was a major cholera epidemic in London that lasted 22 years and has been called the “Great Stench†period.
As in many urban cities of the time, London was overcrowded and lacked good sanitation, which was an ideal breeding ground for disease. In August 1854, a major cholera epidemic struck the district of Soho in London. Dr John Snow, an English physician, did not believe in the miasma theory and hypothesized that the disease was spread through contaminated drinking water.
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Cholera from contaminated water
Without an effective sewage system, all waste was dumped into the Thames, London’s source of drinking water. Dr Snow showed that two water companies took water from sewage-polluted sections of the Thames and delivered the water to homes with higher cholera incidence.
He went door to door asking questions and ultimately speculated that the source of the disease could be the Broad Street public water pump in Soho. As an emerging epidemiologist, Dr Snow had discerned that death rates were proportional to proximity to that particular pump. When he convinced the city council to remove the handle from the pump, the cholera rate improved dramatically.
The use of statistical methods by Dr John Snow and his case study can be considered as the founding event of the world of epidemiology.
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Robert Koch and the germ theory of disease
In 1883, Robert Koch, a bacteriologist in London, finally identified the specific germ of cholera: the cholera bacillus.
One of the most influential bacteriologists in history, Koch also proved that microorganisms cause anthrax and tuberculosis. His work was important in proving the germ theory of disease and that diseases were contagious.
Development of germ theory
With the help of Robert Koch, Edward Jenner, and later Louis Pasteur, the germ theory began to be refined in the mid-19th century. He said that specific microorganisms are the cause of specific diseases.
This theory radically changed the practice of medicine. Scientific evidence for this theory has been provided by the laboratory research of Louis Pasteur and Robert Koch. Together, their work has led to research that has identified dangerous germs and developed life-saving treatments.
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Louis Pasteur and modern medicine
Some of Louis Pasteur’s early work was with wine growers in France, trying to determine the cause of grape blight.
Pasteur has shown that wine diseases are caused by microorganisms that can be killed by heating wine to 55 degrees Celsius for several minutes. This is why the process has been named “pasteurization”.
He also found that beer and milk spoiled due to the rapid multiplication of microbes in these liquids, and this could be avoided through pasteurization.
Pasteur discovers vaccines
For his work, Pasteur subsequently obtained a US patent “for the improvement of the pasteurization of beer and ale”. In 1885, Pasteur discovered vaccines against chicken cholera, anthrax and even the first vaccine against the rabies virus.
Since rabies is one of the most consistently fatal infectious diseases, the rabies vaccine has important implications. Rabies was too small to be seen under any microscope at the time, which led to the concept of smaller organisms, known as viruses. Louis Pasteur created the Institut Pasteur which encouraged the freedom of the creative imagination and rigorous scientific experimentation.
The Chamberland-Pasteur filter
Pasteur worked with another scientist, Charles Chamberland, to invent a device that would improve virus discovery. In 1884, the Chamberland-Pasteur filter was developed, which completely removed all bacteria from a liquid suspension.
In doing so, the scientists were able to prove that an unknown infectious substance remained in the liquid and passed through the smaller saddle filters. Therefore, they speculated on the existence of viruses even before they were seen.
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The Electronic Microscope
The invention of the electron microscope in the 1930s allowed scientists to finally see viruses, which are about 100 times smaller than bacteria. In order for this microscope to work, electrons, which are subatomic particles, are accelerated in 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 electron bombardment, so the microscope cannot show the dynamic life process of the organism.
Many of the worst illnesses have been found to be caused by specific bacterial or viral pathogens. Vaccines were produced against some of the organisms and by the 1950s antibiotics began 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
Dr John Snow hypothesized that cholera spread through contaminated drinking water.
In 1883, Robert Koch, a bacteriologist in London, identified the cholera germ — cholera bacillus.
The term “pasteurizationâ€Was born when Louis Pasteur demonstrated that wine diseases are caused by microorganisms that can be killed by heating wine to 55 degrees Celsius for several minutes.