Cholera

Vibrio cholerae, better known as the silent killer

In 1854, a major epidemic struck London that would kill hundreds of residents in a short span of time. The disease was better known as cholera, and was not new to London since an outbreak had happened in 1831. Cholera, also known as Vibrio cholerae, is transmitted through water.

Cholera can cause:

Ð'* Diarrhea Ð'- Early on will be fecal, but afterwards painless, massive "rice water stool" which contributes to large amounts of fluid loss

Ð'* Vomiting Ð'- Also contributes to mass amounts of fluid loss

Ð'* Dehydration Ð'- With diarrhea and vomiting combined these two movements lead to dehydration. Over 1/5 of a person's entire body weight can be lost in a single day.

Ð'* Death Ð'- If the body's water and electrolytes are not replenished rapidly within 12 hours, death may occur due to severe dehydration.

Although cholera stunned many continents in the 1800's the immediate cause was unknown at the time. It was believed that cholera was transmitted through the air, but its cause was not known due to the lack of research done on the disease. Dr. John Snow would become known as the "Father of Modern Epidemiology for his hard work and research on the cholera epidemics that struck London in 1831 and 1854.

In 1831, John Snow was the age of eighteen and worked as an apprentice for Dr. Hardcastle when London experienced its first tasting of the cholera disease. Snow was sent to treat patients, who were mostly coal miners, but there was not much he could do to help them. The epidemic ended as soon as it started in 1832, and Snow continued to work on his M.D. degree for the next sixteen years.

Theories explaining the cause of cholera

The "Miasma" theory was believed by many doctors to be the explanation of the spread of cholera and many other diseases in the nineteenth century. The theory stressed eradication of disease through the preventive approach of cleansing and scouring, rather than through the purer scientific approach of microbiology. Dr. William Farr was very supportive of this theory and reasoned that soil at low elevations, especially near the banks of the River Thames, contained much organic matter, which produces miasmata. The concentration of such deadly miasmata would be greater at lower elevations than in communities in the surrounding hills. Dr. Farr produced a graph to support his theory (as shown in Figure 1). Dr. Farr believed firmly in his theory until Dr. Snow's research was published, then his mind would be changed.

Figure 1 - The death rates for cholera seem to relate to the Miasma theory, but later on Dr. Farr's findings would be mere coincidence because the theory would be proved wrong later on.

The second theory was that of spontaneous generation of disease within the blood called the blood generation theory. This theory was essentially chemical, and as such, denied contagion. The most active supporter of the theory was the German chemist Justus von Liebig who held strong views on "fermentation" of the blood. The blood generation theory received negligible support in England.

The "Germ" Theory, which was supported by John Snow, theorized that cholera was caused by a germ cell. Snow did not know the exact germ cell that caused cholera, but believed that the germ was transmitted from person to person through contaminated drinking water. Many other peers, but especially Dr. John Simon (head medical officer of London), deemed Snow's theory peculiar.

Cholera Outbreak starting in 1848

Dr. Snow was thirty-five and another outbreak of cholera had surfaced in London. Snow had been waiting for another outbreak of cholera to happen, and would be tracking its every step. The first victim of the outbreak had been a merchant seaman who was stopping in London for a break and rented a room in the city. The seaman developed symptoms of cholera and died shortly thereafter. Snow's germ theory was supported when he learned that a second gentleman had rented the same room where the seaman died.

Snow believed that the room was not thoroughly cleaned and the germs remained in the room, possibly in the bed linen. As more and more patients were examined, Snow noticed many of them were complaining of digestive problems, which would mean that the germ had to be ingested. These finding proved the Miasma theory to be weak, because if the theory were true, the patients would be complaining about their lungs or nasal passages hurting and not their digestive systems.

In the summer of 1849, the second year of the recent cholera outbreak, Snow decided to share what he considered convincing evidence that cholera was being spread through contaminated water. With his own money, Snow published a pamphlet entitled On the Mode of Communication of Cholera, which was a thirty-nine page pamphlet explaining his evidence to support his theory. Snow provided many examples to explain that if the cholera disease was to be eliminated, drinking water was going to have to be isolated from sewage water. To avoid criticisms by other physicians, Snow did not elaborate that this germ was a living organism. He wrote that this was a poison that had the ability to multiply itself within the digestive tracts of its victims before it was spread to new future casualties.

When cholera broke out the following summer, Snow suspected a contaminated pipe coming from the Thames River was causing the spread of cholera. After looking through the municipal records, Dr. Snow found that two private water companies were supplying water into the district where Snow had lived.

The Grand Experiment

Lambeth Water Company and Southwark and Vauxhall Water Company were two water companies supplying the water for Snow's district. The Southwark and Vauxhall Water Company, was drawing water from an area along the Thames that was known to be polluted by sewage, whereas the other company, the Lambeth Water Company, had recently moved its intake facilities to a location above the sewer outlets. Snow compared the two sources of water with the mortality rates of consumers and came up with some hard evidence. The Lambeth Water Company had changed its intake from opposite Hungerford Market to Thames Ditton [boiling Wells], thus obtaining a supply of water quite free from the sewage of London.

Even though Lambeth moved to a much cleaner intake structure, Vauxhall stayed with

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