M.  Chairman


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.




(from Book Reviews of The Ghost Map, appearing in various editions of Lancet,NEJM, BMJ, JAMA, in 2006)