AN EPIDEMIOLOGIC CLASSIC
SNOW ON CHOLERA
Dr. John Snow (1813-1858) was a distinguished British anesthesiologist who,
among other accomplishments, administered chloroform to Queen Victoria at the birth
of two of her children.
His lasting fame, however, is based on his brilliant work
elucidating the epidemiology of cholera.
The following material consists of excerpts from Snow's classic monograph "On
the Mode of Communication of Cholera," Second Edition, 1854 (Snow on Cholera.
Haffner, New York, 1965). The entire monograph is fascinating reading, but enough is
contained in the portions presented below to give the flavor of the original and to permit
the reader to see the type of evidence collected by Snow and the way in which he
Read the selections of Snow's work that follow, bearing in mind that the
infectious theory of disease was not generally accepted at the time.
usually believed to be caused by morbid poisons coming from dead bodies and
decaying organic matter in effluvia, and spread through the air.
"The existence of Asiatic Cholera cannot be distinctly traced back further than the
It would occupy a long time to give an account of the progress of cholera over
different parts of the world, with the devastation it has caused in some places, whilst it
has passed lightly over others, or left them untouched; and unless this account could be
accompanied with a description of the physical condition of the places, and the habits of
the people, which I am unable to give, it would be of little use.
"There are certain circumstances, however, connected with the progress of
cholera, which may be stated in a general way.
it travels along the great tracks of
human intercourse, never going faster than people travel, and generally much more
In extending to a fresh island or continent, it always appears first at a sea-port.
It never attacks the crews of ships going from a country free from cholera, to one where
the disease is prevailing, till they have entered a port, or had intercourse with the shore.
Its exact progress from town to town cannot always be traced; but it has never
appeared except where there has been ample opportunity for it to be conveyed by