Transcript Cholera

Cholera - History
Dr Andrew Hayward Lecturer - Epidemiology
and Public Health
University of NottinghamUK
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
• Cholera pandemics 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.
• 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.
A case of true cholera
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