London, England in 1854
was a virtual sea of human and animal waste,
and as a result.... it stank.
In fact, the year 1854...was referred to as the year of the "Great Stink".
The problem was...
that there were two and a half million people crammed
into a 30-mile circumference in the City,
The London district of Soho was more densely populated
than modern Manhattan.
that there was no safe means of sewage disposal ...for all these people.
Sewage... was simply pitched out
in the gutters and ditches alongside the streets,
and from there, the nasty stuff flowed into the Thames River
which was therefore highly polluted.
So London at that time
was a sitting duck for epidemics of.. infectious disease.
And one of the most feared infectious diseases
of the time was ...Cholera.
The cause of Cholera , was unknown at that time.
In 1853 there were two theories
as to what caused the disease.
The "miasma"theory ...was that it had to do with.... bad air...
The disease was somehow transmitted through the air.
The other theory of the time was
the "contagion" theory ....
wehich held that Cholera was transmitted directly
from person to person.
Both theories.... were ultimately proven to be incorrect.
but it was not until ...30 years later that
Dr. Robert Koch.... discovered the actual Cholera bacteria,
snd it was then realized... that the disease...
was in fact transmitted through.... drinking water
which had been contaminated by sewage.
Now enter ....into all of this scientific confusion,
Dr. John Snow.
Born in 1813
he was ...A vegetarian and teetotaler,
and he established a medical practice in London.
He was very successful ...as his general practice,
and he also had an interest...in anaesthesia,
which had just been introduced.
In fact in 1853, Snow himself administered chloroform
to Queen Victoria....for the birth of her eighth child.
But Snow's real fame....was achieved
a little later the same year...
when he did something amazing.
That year, Dr. John Snow, almost singlehandedly,
wthout any support from the medical establishment,
tracked down.... the cause
of the cholera epidemic.... in London.
Snow's interest in cholera began
when he saw first saw cholera patients ...
while he was a physician's apprentice
during the first epidemic 1832 in England,
which killed 32,000,
and his interest was rekindled during the outbreak of 1848,
which killed 52,000.
A series of cases that he saw....and other observations that he made
led Snow to hypothesize... that the disease
was spread from person to person ....by mouth
and most likely through..... water.
Snow described his conclusions ...in an 1849 publication,
but this publication was ignored .....by the medical establishment.
What Snow needed ....was more evidence.
Well, his opportunity came.....in the summer of 1854,
when cases of cholera began occurring
mainly among people who lived... along the Thames River in London
Water supply in London ...was a privatized service at the time.
There were two water supply companies in the City...
the Lambeth Water Company ....and the Vauxhall Water Company -
both of which drew their water
from the most polluted part of the river.
However in 1852 the Lambeth company..
relocated its supply source
to the Thames river north of London,
where it was not polluted by sewage from the City.
So Snow decided to do a Survey
to compare the incidence of cholera
between the two groups of people,
which included a total population ....of about 300,000.
Now Snow did not do this .....by sitting at a computer station
at the local Health Unit....as it would be done now.
His method was the old fashioned.. "shoe leather " technique.
Both of these water companies ...competed for business
in each neighbourhood,
so Snow had to walk from house to house
to determine which company supplied ...each household's water.
And by doing this.....by walking from house to house,
and knocking on each door....Snow found that
40 000 houses were supplied by..... the Vauxhall company
And 26,000 houses were supplied ...by the Lambeth company.
When he added up the numbers
lo and behold ...he found the death rate from cholera
of the Vauxhall customers
was 8 times higher .....than the death rate
amongst the Lambeth customers.
(315 per 10,000 houses vs 37 per 10,000)
So this evidence certainly supported... his theory.
And then, the next thing that happened
was right in Snow's own neighborhood
near Golden Square in Soho.
Cholera rates suddenly exploded there
....the disease was out of control -
197 residents died in 3 days.
So once again, Snow put on his boots
and got out into the streets...walking from house to house.
He marked the houses ...where the deaths had occurred
on a map.....which became known as
"The Ghost Map" ...which showed the distribution of the disease.
And this is exactly what the science of Epidemiology is..
It is the study of the distribution of disease.
So if you want to remember what Epidemiology is
just think of Snow's ghost map.
The result was.... that the map showed
that 61 of the 83 people who died
had obtained their water..
from the public water pump.... on Broad Street in Soho.
So here was...a smoking gun.
This particular pump....was obviously
the source of the outbreak.
Then Snow made one more clever observation.
He noted, that rather curiously,
none of the 70 employees
of the Lion Brewery .......which was located
on a few yards from the Broad Street water pump
... got cholera.
Why would this be?
Well , it was a case of the exception proving the rule.
Snow found out that all of the employees
who worked at the Lion Brewery
were generously provided ...by their employer...
with free access to malt liquor....the bar was always open.
So these people rarely, if ever, drank water
and as a consequence...they never contracted Cholera.
Well, all of this evidence that Snow had gathered
in support of his theory
of the water-borne transmission of Cholera
was now overwhelming.
Even the skeptical members
of the Board of Governors of St. James Parish
were now convinced......and they finally took action.
On September 8, 1854,
one week after the outbreak had begun.
they removed the handle
of the Broad Street public water pump
thereby closing it down,
The Cholera outbreak was stopped in its tracks.
John Snow died of a stroke at age 45,
before his work was fully appreciated.
In fact his obituary in the Lancet
did not even mention his cholera research.
But ultimately all of this evidence was too much
for the medical establishment to ignore.
As a consequence of his boots on the ground, shoe leather science
Snow became recognized as
the founding father ....of the science of Epidemiology.
So.....well before the scientific proof
of the germ theory of disease was even discovered,
General practitioner Dr. John Snow....
had ingeniously tracked down,
and crushed.......a killing epidemic
of the dread disease ....of Cholera.