1. John Snow web-site - UCLA
Cholera - History
Dr Andrew Hayward - Lecturer - Epidemiology and Public Health University of Nottingham- UK
WHO Cholera Fact sheet
John Snow web-site - UCLA

2. Dr Andrew Hayward
I am an epidemiologist who is particularly interested in the epidemiology of infectious disease. It’s easy to forget how diseases like cholera used to be so important even in rich countries. The disease provides a unique insight into the power of a public health approach.
As well as being interested in the epidemiology of infectious diseases in the modern world, I am fascinated by their historical impact. This presentation contains many links to historical images.

3. Learning Objectives
To understand the historical background to John Snow’s work on cholera.
To understand how John Snow used epidemiology to determine the cause of cholera.
To understand how this led to disease prevention on a massive scale.

4. Performance Objectives
To be able to find and use information related to cholera and other water-born diseases.

5. Severe disease in around 5%
Vibrio cholerae.
Often mild symptoms
Severe disease in around 5%
Profuse watery diarrhoea, vomiting, and leg cramps. Rapid dehydration and shock.
Without treatment, death can occur within hours.
Cholera is an acute, diarrhoeal illness caused by infection of the intestine with the bacterium Vibrio cholerae. The infection is often mild or without symptoms, but sometimes it can be severe. Approximately one in 20 infected persons has severe disease characterized by profuse watery diarrhoea, vomiting, and leg cramps. In these persons, rapid loss of body fluids leads to dehydration and shock. Without treatment, death can occur within hours.

6. Cholera pandemics spread around the globe
Pandemics of cholera
Cholera pandemics spread around the globe
Most have started in the Indian Subcontinent
The most recent started in 1961
Since the 1800’s cholera pandemics have spread around the globe The link shows a map illustrating the spread during one pandemic. Most have started in the Indian Subcontinent. The most recent started in 1961 and is still on-going having affected at least 100 countries.

7. Cholera sufferers are dehydrated and often have deep sunken eyes.
Cholera pandemics caused great fear and changed history. “Cholera tramples the victor and the vanquished both”.
The links show an etching of a cholera patient and a cartoon illustrating how cholera could devastate both sides in a battle.

8. Beliefs about the causes of cholera
Supernatural causes
The wrath of God
Astrological causes
Miasma - or “bad air”
Contagion
Prior to the work of John Snow people had very little concept of mechanisms of contagion. Consequently beliefs about the causes of cholera were often bizzare. The link shows an etching of a Figure of Death, wearing a robe and dancing slippers, playing a fiddle of human bones. The bodies of partygoers litter the dance floor as the musicians fearfully exit, instruments in hand.

9. Miasma - bad or malodorous air as a cause of disease.
Pleasant or strong smelling agents (e.g. Camphor, herbs, or smoke) were thought to be protective.
The belief in Miasma led people to try and protect themselves against the disease with substances that would counteract bad smells. The illustrations show people buying camphor, a lady wearing protective clothing covered in sweet smelling herbs and a man smoking a large cigar in order to ward off cholera.

10. Miasma
Public health efforts concentrated on finding the source of bad smells.
Because of the Miasma theory public health efforts concentrated on finding the source of bad smells (e.g. heaps of manure) and removing them. Public health officials in London were paid to do this. The cartoon shows inspectors searching for smells in London. It’s worth having a close look to read their comments!

11. Protection against cholera
Many believed that alcohol would protect against cholera.
The link shows a child being made to drink brandy to ward off cholera. She is surrounded by drunken people.

12. There was some perception that disease could be spread by contact with the patient or contact with their clothes (fomites). Fumigation of premises was thought to be valuable.
The link shows a cartoon of doctors with a patient they suspect of having cholera. Note he is bundled up in sheets to prevent spread, one doctor is holding up his dirty trousers with a stick and one is recommending that the house be fumigated. The patient believes this is all unnecessary because he only has a cold! It is worth having a close look to read the comments.
A case of true cholera

13. Cholera epidemics in England
,000 deaths
,000 deaths
John Snow’s work
It was against this background of confusion that John Snow carried out his work.
John Snow was already a famous anaesthetist and had been one of the first to use chloroform. He had even administered it to Queen Victoria. He carried out his work in London during the third large epidemic of cholera in England. Prior to his work there was complete confusion about the cause of cholera as illustrated in the previous slides. His work on cholera has led him to be called “The father of epidemiology”. The link shows a photograph of John Snow.

14. John Snow mapped cases of cholera to help give him clues about the cause.
During the outbreak, John Snow carefully mapped cases of cholera in one area of London which was particularly badly affected. (The SOHO area of London). Cases appeared to be clustered around a water pump on Broad Street. Click on the map to take a closer look.

15. He found that those who were affected had drunk water from the pump.
Broad Street Pump
Mapping of cases led John snow to suspect water from the Broad street pump as a cause of cholera.
He found that those who were affected had drunk water from the pump.
John Snow identified that workers at a local brewery did not get cholera - they had their own water supply and a free beer allowance!
He found that a family who had moved away from the area but still drank from the pump because they liked the taste also became ill.

16. Broad Street Pump
He identified that a child at number 40 Broad street had been ill with cholera and that sewage had probably contaminated the well.

17. Removal of the pump handle.
John Snow recommended the pump should not be used and that it’s handle should be removed.
“I had an interview with the Board of Guardians of St. James's parish, on the evening of Thursday, 7th September, and represented the above circumstances to them. In consequence of what I said, the handle of the pump was removed on the following day." Quote from John Snow.
The link shows more information about the pump including a photograph of a replica on Broad Street with it’s handle removed.

18. The outbreak subsided.
After the handle was removed the outbreak subsided.
Despite this there was scepticism about his findings.
Although the numbers of cases had already began to decline it is likely that the removal of the pump handle prevented another outbreak - around the same time as the pump handle was removed the father of the child at 40 Broad street also became ill - his faeces would have contaminated the well and probably led to another outbreak.
General Board of Health Report 1854.
“We do not find it established that the water was contaminated in the manner alleged; nor is there before us any sufficient evidence to show whether inhabitants of the district, drinking from the well suffered in proportion more than other inhabitants of the district who drank from other sources.”

19. The Grand Experiment
Two water companies supplied one area. In 1949 both got water direct from the Thames in London. In 1954 the Lambeth Company moved it’s source upstream to cleaner water.
John Snow overcame this scepticism by conducting an elegant epidemiological study which he called "The Grand Experiment"
Quote from John Snow - “The experiment, too, was on the grandest scale. No fewer than three hundred thousand people of both sexes, of every age and occupation, and of every rank and station, from gentlefolks down to the very poor, were divided into two groups without their choice, and, in most cases, without their knowledge; one group being supplied with water containing the sewage of London, and, amongst it, whatever might have come from the cholera patients, the other group having water quite free from such impurity”

20. Comparison of risks of dying from cholera
Southwark and Vauxhall water company 70 per 10,000 (London Source)
Lambeth water company 5 per 10,000 - (Source from upstream of London)
He compared annual death rates from cholera in people drinking water from different sources and found that the risk was 14 times greater (relative risk 14) in those who drank water which was extracted from the Thames in London where there was heavy sewage contamination.
He concluded that cholera was spread from person to person via morbid material from the alimentary canal of the sufferer that was then swallowed by other people and had the power of multiplication in the body of the person it attacked.

21. Massive public concern and sanitary reform followed.
,000 deaths
,000 deaths
John Snow’s work
Massive public concern and sanitary reform followed.
Final epidemic was in 1866 there were only around 2,200 deaths.
John Snow’s work led to massive public concern about contamination of drinking water. This is clearly illustrated by a cartoon of the time (follow link - It's worth having a close look to read the comments). Massive sanitary reform followed which prevented future epidemics of cholera. The last epidemic was in 1866 and was much smaller than previous epidemics. The link shows an animation of the spread of the 1886 epidemic in London.

22. Vibrio Cholera
The organism that causes cholera was discovered 25 years after John Snow’s death by Robert Koch
The first link shows electron micrographs of Vibrio Cholera and information about the organism. In addition to discovering the causative organism for cholera, Koch also discovered the causative organisms for tuberculosis and anthrax. His achievements were so well recognised they were even celebrated on Chocolate boxes! (see second link).
However, even though the causative organism was not known prior to Koch, John Snow’s epidemiological work allowed preventative action to be taken saving many many thousands of lives.

23. Cholera remains a serious problem in many countries.
Poor access to safe water and inadequate disposal of sewage in resource poor countries is the main reason.
Despite our knowledge of the cause of cholera a high proportion of the world’s population still does not have access to safe water or facilities for disposal of excreta. This allows epidemics to continue to spread. The link is to a British Charity - WATERAID which is trying to help with this problem.

24. Did you come into medicine to save lives?
If the answer is yes - perhaps you should give up medical school and take a course in water engineering.
Find out more about cholera and water supplies in the modern world in the following slides.

25. WHO fact sheet on Cholera
Find out more facts about cholera by accessing the latest WHO fact sheet.
WHO fact sheet on Cholera
Access the WHO fact sheet and use it to answer the following questions.
How many cholera pandemics have there been?
What cholera sub-type is causing the current pandemic?
Where did it start?
What is the fatality rate?

26. Find out where the latest cholera epidemic is.
Latest Cholera Epidemics - WHO

27. WHO figures on safe drinking water and sanitation
Find out what proportion of the world have access to safe water and safe facilities for excreta disposal.
Follow the link to answer the following questions.
In 1994 what proportion of Africa’s population had access to safe drinking water/sanitation? What was the proportion in rural areas?
WHO figures on safe drinking water and sanitation

28. Find out about deaths from diarrhoeal disease in 1998.
WHO estimates of causes of death
Follow the link to answer the following questions.
What proportion of all deaths were due to diarrhoeal disease in 1998?
What was the proportion in high income countries?
What was the proportion in middle/low income countries?

29. Find out how many cases of cholera were reported to WHO last year.
WHO figures on Cholera
Follow the link to answer the following questions.
How many cases were reported in Africa? How many deaths?
How many cases were reported in Europe?
Do you think these reported cases are likely to represent all the cases that occurred?

30. Find out how much it costs to build a safe well or toilet in Africa.
WATERAID
Follow the link to find out how much it costs WATERAID to build a well to provide safe drinking water in Africa.

31. Other routes of transmission of cholera
This is a picture of your lecturer about to eat raw clams in Mexico (delicious!). Find out why this was a risky idea by clicking on the picture.

32. Learn more about epidemiology and control of diarrhoeal disease.
Supercourse Lecture