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Epidemiology and Cholera

Cholera is still a problem in some parts of the world

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What is cholera? ...all is darkness and confusion, vague theory, and a vain speculation. Is it a fungus, an insect, a miasma, an electrical disturbance, a deficiency of ozone, a morbid off-scouring from the intestinal canal?

We know nothing; we are at sea in a whirlpool of conjecture.

- Wakley T. The Lancet II, 393, 1853

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English physician and a leader in the adoption of anaesthesia and medical hygiene.

He is considered to be one of the fathers of epidemiology, because of his work in tracing the source of a cholera outbreak in Soho, England, in 1854.

Wikipedia

http://www.ph.ucla.edu/epi/snow.html#BROAD

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Original Snow map of Soho, England during the 1854 cholera outbreak

showing the individual cases of cholera

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During the next three days, 127 people living in or around Broad Street died. Few families, rich or poor, were spared the loss of at least one member. Within a week, three-quarters of the residents had fled from their homes, leaving their shops shuttered, their houses locked and the streets deserted. Only those who could not afford to leave remained there. It was like the Great Plague all over again.

By 10 September, the number of fatal attacks had reached 500 and the death rate of the St Anne's, Berwick Street and Golden Square subdivisions of the parish had risen to 12.8 per cent -- more than double that for the rest of London.

From Judith Summers in her history of the Soho neighborhood of London.

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He traced the outbreak in South London to contaminated water supplied by the Vauxhall Water Company -- a theory that the authorities and the water company itself were, not surprisingly, reluctant to believe.

Now he saw his chance to prove his theories once and for all, by linking the Soho outbreak to a single source of polluted water.

His research led him to a pump on the corner of Broad Street and Cambridge Street, at the epicenter of the epidemic.

"I found," he wrote afterwards, "that nearly all the deaths had taken place within a short distance of the pump." In fact, in houses much nearer another pump, there had only been 10 deaths -- and of those, five victims had always drunk the water from the Broad Street pump, and three were schoolchildren who had probably drunk from the pump on their way to school.

From Judith Summers in her history of the Soho neighborhood of London.

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Lambeth Water Company

(water obtained upstream from

London) – 5 per 100,000

Southwark and Vauxhall Water Company (water obtained from

London) – 70 per 100,000

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He took his findings to the Board of Guardians of St James's Parish, in whose parish the pump fell.

Though they were reluctant to believe him, they agreed to remove the pump handle as an experiment. When they did so, the spread of cholera dramatically stopped. [actually the outbreak had already lessened for several days]

There were several unexplained deaths from cholera that did not at first appear to be linked to the Broad Street pump water -- notably, a widow living in West End, Hampstead, who had died of cholera on 2 September, and her niece, who lived in Islington, who had succumbed with the same symptoms the following day. Since neither of these women had been near Soho for a long time, Dr Snow rode up to Hampstead to interview the widow's son. He discovered from him that the widow had once lived in Broad Street, and that she had liked the taste of the well-water there so much that she had sent her servant down to Soho every day to bring back a large bottle of it for her by cart. The last bottle of water -- which her niece had also drunk from -- had been fetched on 31 August, at the very start of the Soho epidemic.

From Judith Summers in her history of the Soho neighborhood of London.

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So what had caused the cholera outbreak?

The Reverend Henry Whitehead, vicar of St Luke's church, Berwick Street, believed that it had been caused by divine intervention, and he undertook his own report on the epidemic in order to prove his point. However, his findings merely confirmed what Snow had claimed, a fact that he was honest enough to own up to.

Furthermore, Whitehead helped Snow to isolate a single probable cause of the whole infection: just before the Soho epidemic had occurred, a child living at number 40 Broad Street had been taken ill with cholera symptoms, and its nappies (diapers) had been steeped in water which was subsequently tipped into a leaking cesspool situated only three feet from the Broad Street well.

From Judith Summers in her history of the Soho neighborhood of London.

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Gro Harlem Brundtland, M.D., M.P.H. former Director-General, World Health OrganizationGeneva, Switzerland

In Washington, D.C., 28 October 1998

"In historic terms the marriage between science and health is a relatively recent event. Not long ago superstition, magic and astrology were the only weapons our ancestors had to fight diseases and epidemics that haunted the world. They were seen as divine punishments or unfavorable influence of the heavenly bodies."

"We owe that marriage to the creators of modern bacteriology, epidemiology and therapeutics - to scientists such as Louis Pasteur, Robert Koch, John Snow, Alexander Fleming and Paul Erlich - and their discoveries that shaped modern medicine and public health policies. They helped rescue our civilization from the dark ages of the unknown - and the unknown had names such as plagues, cholera or syphilis."

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Cholera is still here

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Cholera

David A Sack, R Bradley Sack, G Balakrish Nair, A K Siddique Intestinal infection with Vibrio cholerae results in the loss of large volumes of watery stool, leading to severe and rapidly progressing dehydration and shock. Without adequate and appropriate rehydration therapy, severe cholera kills about half of affected individuals. Cholera toxin, a potent stimulator of adenylate cyclase, causes the intestine to secrete watery fluid rich in sodium, bicarbonate, and potassium, in volumes far exceeding the intestinal absorptive capacity.

Cholera has spread from the Indian subcontinent where it is endemic to involve nearly the whole world seven times during the past 185 years. V cholerae serogroup O1, biotype El Tor, has moved from Asia to cause pandemic disease in Africa and South America during the past 35 years. A new serogroup, O139, appeared in south Asia in 1992, has become endemic there, and threatens to start the next pandemic. Research on case management of cholera led to the development of rehydration therapy for dehydrating diarrhoea in general, including the proper use of intravenous and oral rehydration solutions.

Appropriate case management has reduced deaths from diarrhoeal disease by an estimated 3 million per year compared with 20 years ago. Vaccination was thought to have no role for cholera, but new oral vaccines are showing great promise.

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