7/29/2019 Jg epi

1/7

1

TAUREAN COWAN- 00038320

EPIDEMIOLOGY

THE CONTRIBUTIONS OF

JOHN GRAUNT, WILLIAM FARR, JOHN SNOW

TO EPIDEMIOLOGY

7/29/2019 Jg epi

2/7

2

JOHN GRAUNT

John Graunt, was a London tradesman and founding member of the Royal Society of London.

He was a pioneer in terms of applying the idea that the physical universe followed a specific

pattern referred to as laws, to biology with the belief that there are patterns to death and disease.

He is thought of as the first to become an epidemiologist, statistician, and demographer when he

summarized the Bills of Mortality for his 1662 publicationNatural and Political Observations

Mentioned in a Following Index, and Made Upon the Bills of Mortality. This was an analysis of

weekly bills of death and its causes in London which was done in an attempt to look at the

phenomena over a period of time beginning from1592.

He developed methods for analysing the data and in the process created a new framework

within which the analysis of other statistical data would fit and further progress. His method was

a novel way of approaching data and took the form of first critically examining the sources and

attempting to address issues of bias in recording data, second using frequencies and ratios rather

than absolute numbers in his analysis, which allowed for greater flexibility and thus for a

number of correct comparisons to be made and third applying methods to tackle concrete

problems.

.

As such Graunt was able to make a number of deductions about fertility, morbidity,

and mortality . For instance he took note of new diseases such as rickets, and made a number of

observations for example

_ Some diseases affected a similar number of people from year to year, while others varied

considerably over time.

7/29/2019 Jg epi

3/7

3

_ Common causes of death included old age, consumption, smallpox, plague, and diseases of

teeth and worms.

_Many greatly feared causes of death were actually uncommon, including leprosy, suicide, and

starvation.

_ Four separate periods of increased mortality caused by theplague occurred from 1592 to 1660.

_ The mortality rate for men was higher than for women.(

Graunt was the first to assess the number of inhabitants, age structure of the population, and rate

of population growth in London. He was also the first to construct a life table that summarized

patterns of mortality and survival from birth until death . He was thus able to infer that the rate of

mortality for children was relatively high noting that only 25 individuals out of 100 survived to

age 26 years. Further, he deduced that, though mortality rates for adults were much lower, very

few people reached old age (only 3 of 100 London residents survived to age 66 years).

Although Graunt referred to his work a mere reduction of confused volumes into tables and

observations historians consider his work much more significant. According to Statistician

Walter Willcox Graunt is memorable mainly because he discovered the numerical regularityof

deaths and births, of ratios of the sexes at death and birth, and of the proportion of deaths from

certain causes to all causes in successive years and in different areas; or in general terms, the

uniformity and predictability of many important biological phenomena taken in the mass. In

doing so, he opened the way both for the later discovery of uniformities in many social and

volitional phenomena like marriage, suicide and crime, and for a study of these uniformities,

their nature and their limits.(Jones &Bartlett)

7/29/2019 Jg epi

4/7

4

WILLIAM FARR

William Farr built upon Graunts work in the mid-1800s, when William Farr began a process of

collecting and analyzing Britains mortality statistics with the introduction of a national system

of recording causes of death.

He is considered the father of modern vital statistics and surveillance, because of his

development of many of the basic practices used today in vital statistics and disease

classification. He extended the epidemiologic analysis of morbidity and mortality data, looking

at the effects of marital status, occupation, and altitude. He also developed many epidemiologic

concepts and techniques still in use today.

Farr birthed a variety of activities encompassed by modern epidemiology. He described the state

of health of the population, he sought to establish the determinants of public health, and he

applied the knowledge gained to the prevention and control of disease.

Farr made several practical and methodological contributions to the field of epidemiology. The

first of which is that he strove to ensure that the collected data were accurate and complete.

Second, he devised a categorization system for the causes of death so that these data could be

reduced to a usable form. The system that he devised is the antecedent of the modern

International Classification of Diseases, which categorizes diseases and causes of death. Third,

Farr made a number of important contributions to the analysis of data, including the invention of

the standardized mortality rate, an adjustment method for making fair comparisons between

groups with different age structures. With his sound method he was able to make a number of

inferences. An example being that Decreases in mortality rates followed improvements in

sanitation. Based on these inferences he was able to form a number of hypotheses about the

causes and preventions of disease For example, he used data on smallpox deaths to derive a

7/29/2019 Jg epi

5/7

5

general law of epidemics that accurately predicted the decline of the rinderpest epidemic in the

1860s

JOHN SNOW

John Snow was an anesthesiologist who conducted a series of investigations in London that later

earned him the title the father of field epidemiology. Some twenty years before

the advent of the microscope, Snow conducted studies of cholera outbreaks both to

discover the cause of disease and to prevent its recurrence. the methods used in his work

classically illustrates the sequence from descriptive epidemiology to hypothesis generation to

hypothesis testing (analytic epidemiology) to application..

John Snow conducted his classic study in 1854 when an epidemic of cholera developed in the

Golden Square of London. He began his investigation by determining where in this area persons

with cholera lived and worked. He then based on the information gatheredhe was able map the

distribution of cases on what epidemiologists call a spot map.

Working with the hypothesis that cholera was spread via water and that there was a relationship

between the location of the pumps and the cases of the disease he investigated its occurrence.

What he found was that there was one common factor among the afflicted they had all consumed

water from the broad street pump.

in 1854 there was another outbreak of cholera in London which prompted another investigation.

He had already done the first study on cholera and had noted water as the source of the disease

and that certain districts with the highest recorded mortalities had water supplied by two

companies- the Lambeth Company and the Southwark and Vauxhall Company. Both companies

obtained water from the Thames River, at intake points that were below London. However in

1852, the Lambeth Company moved their water works to above London, thus obtaining water

7/29/2019 Jg epi

6/7

6

that was free of London sewage. This time however he was afforded a chance for greater

comparison of the districts as the Lambeth company had relocated its intake point above London

and thus free from sewage that contaminated the water supplied by the Southwark and Vauxhall

Company. He was able to infer that the risk of death from cholera was more than 5 times higher

in districts served only by the Southwark and Vauxhall Company than in those served only by

the Lambeth Company which then proved his hypothesis that, that water obtained from the

Thames below London was a source of cholera.

Based on a characterization of the cases and population at risk by time, place, and person, Snow

developed a testable hypothesis. He then tested this hypothesis with a more rigorously designed

study, ensuring that the groups to be compared were comparable. His methodology provided a

template for field study of the occurrence of disease. For several reasons, Snows

investigations are considered a nearly perfect model for epidemiologic research. First, Snow

organized his observations logically so that meaningful inferences could be derived from them.

Second, he recognized that a natural experiment had occurred in the sub-districts of London

that would enable him to gather unquestionable proof either for or against his hypothesis. Third,

he conducted a quantitative analysis of the data contrasting the occurrence of cholera deaths in

relation to the drinking water company.(Jones &Bartlett)

After this study, efforts to control the epidemic were directed at changing the location of the

water intake of the Southwark and Vauxhall Company to avoid sources of contamination. Thus,

with no knowledge of the existence of microorganisms, Snow demonstrated through

epidemiologic studies that water could serve as a vehicle for transmitting cholera and that

epidemiologic information could be used to direct prompt and appropriate public health action.

7/29/2019 Jg epi

7/7

7

BIBLIOGRAPHY

Aschengrau, A., & Seage, G. R. (2008).Essentials of epidemiology in public health (2nd ed.).

Sudbury, Mass.: Jones and Bartlett Publishers

BBC - History - Historic Figures: John Snow (1813 - 1858). (n.d.). BBC - Homepage. Retrieved

September 29, 2012, from

http://www.bbc.co.uk/history/historic_figures/snow_john.shtml

Celebration: William Farr (18071883)an appreciation on the 200th anniversary of his birth .

(n.d.). Oxford Journals | Medicine | International Journal of Epidemiology. Retrieved

September 29, 2012, from http://ije.oxfordjournals.org/content/36/5/985.full

John. (n.d.). John Snow - a historical giant in epidemiology.Home | UCLA SPH. Retrieved

September 29, 2012, from http://www.ph.ucla.edu/epi/snow.html

(1976). William Farr: Founder of Modern Concepts of Surveillance.International Journal of

Epidemiology, 6, 13-18. Retrieved September 15, 2012, from

http://www.epidemiology.ch/history/PDF%20bg/Langmuir%20AD%201976%20william

%20farr%20-%20founder%20of%20modern%20concept