Cholera - History Dr Andrew Hayward - Lecturer - Epidemiology and Public Health University of Nottingham- UK WHO Cholera Fact sheet John Snow web-site - UCLA
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.
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.
Performance Objectives • To be able to find and use information related to cholera and other water-born diseases.
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.
Pandemics of cholera • Cholerapandemics spread around the globe • Most have started in the Indian Subcontinent • The most recent started in 1961
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”.
Beliefs about the causes of cholera • Supernatural causes • The wrath of God • Astrological causes • Miasma - or “bad air” • Contagion
Miasma • 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.
Miasma • Public health efforts concentrated on finding the source of bad smells.
Protection against cholera • Many believed that alcohol would protect against cholera.
A case of true cholera • 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.
Cholera epidemics in England • 1831-1832 - 22,000 deaths • 1848-1849 - 52,000 deaths • 1853-1854 - John Snow’s work • It was against this background of confusion that John Snow carried out his work.
John Snow mapped cases of cholera to help give him clues about the cause.
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.
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.
Removal of the pump handle. • John Snow recommended the pump should not be used and that it’s handle should be removed.
The outbreak subsided. • After the handle was removed the outbreak subsided. • Despite this there was scepticism about his findings.
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.
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)
1831-1832 - 22,000 deaths • 1848-1849 - 52,000 deaths • 1853-1854 - John Snow’s work • Massive public concern and sanitary reform followed. • Final epidemic was in 1866 there were only around 2,200 deaths.
Vibrio Cholera • The organism that causes cholera was discovered 25 years after John Snow’s death by Robert Koch
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.
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 facts about cholera by accessing the latest WHO fact sheet. • WHO fact sheet on Cholera
Find out where the latest cholera epidemic is. • Latest Cholera Epidemics - WHO
Find out what proportion of the world have access to safe water and safe facilities for excreta disposal. • WHO figures on safe drinking water and sanitation
Find out about deaths from diarrhoeal disease in 1998. • WHO estimates of causes of death
Find out how many cases of cholera were reported to WHO last year. • WHO figures on Cholera
Find out how much it costs to build a safe well or toilet in Africa. • WATERAID
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.
Learn more about epidemiology and control of diarrhoeal disease. • Supercourse Lecture