HISTORICAL_BACKGROUND EPIDEMIOLOGY.pptx

Epidemiology, branch of medical science that studies the distribution of disease in human populations and the factors determining that distribution, chiefly by the use of statistics. Unlike other medical disciplines, epidemiology concerns itself with groups of people rather than individual patients and is frequently retrospective, or historical, in nature. It developed out of the search for causes of human disease in the 19th century, and one of its chief functions remains the identification of populations at high risk for a given disease so that the cause may be identified and preventive measures implemented.

A variety of tools, including mortality rates and incidence and prevalence rates, are used in the field of epidemiology to better understand the characteristics of disease within and across populations. In addition, epidemiologic studies may be classified as descriptive or analytic, depending on whether they are intended to characterize disease or test conclusions drawn from descriptive surveys or laboratory observations. Information from epidemiologic studies frequently is used to plan new health services and to evaluate the overall health status of a given population. In most countries of the world, public-health authorities regularly gather epidemiologic data on specific diseases and mortality rates in their populaces.

The field of epidemiology is highly interdisciplinary. In addition to its close ties to statistics, particularly biostatistics, it relies heavily on the concepts, knowledge, and theories of such disciplines as biology, pathology, and physiology in the health and biomedical sciences as well as on the disciplines of anthropology, psychology, and sociology in the behavioral and social sciences.

Historical development
Epidemiology emerged as a formal science in the 19th century. However, its historical development spanned centuries, in a process that was slow and unsteady and aided by the contributions of many individuals.

One of the first major figures in the historical development of epidemiology was the ancient Greek physician Hippocrates, who is traditionally regarded as the father of medicine. Hippocrates is presumed to have written the Epidemics and On Airs, Waters, and Places, works in which he attempted to explain the occurrence of disease on a rational rather than supernatural basis. Hippocrates recognized disease as a mass phenomenon as well as one affecting individuals.

Another significant contribution to the foundation of epidemiology was made in the 17th century, with the work of English statistician John Graunt. Graunt was the first person to analyze the bills of mortality, which recorded the weekly counts of christenings and deaths in London. In 1662 Graunt published the results of his findings in Natural and Political Observations...Made upon the Bills of Mortality. He found that although male births consistently outnumbered female births, males no longer outnumbered females by the time they reached their

1. PRINCIPLES OF EPIDEMIOLOGY AND DISEASE SURVEILLANCE: HISTORICAL BACKGROUND

2. EVOLUTIONARY PROCESS It has grown from PURE OBSERVATIONS AND ADVICES (Hippocrates) COUNTING OF CASES AND ANALYSIS (John Graunt & William Farr) NATURAL EXPERIMENTS (John Snow) TRUE EXPERIMENTS Lind, Jenner, Fletcher, Doll &Hill & Other epidemiologists in the last two century

3. GROWTH 17 TH -19 TH CENTURIES PERIOD EPIDEMIOLOGIST CONTRIBUTION 1600AD JOHN GRAUNT LONDON BILLS OF MORTALITY ANALYSIS 1747 JAMES LIND CITRUS FRUITS TO CURE SCURVY IN SAILORS 1796 EDWARD JENNER TRIAL WITH COWPOX VACCINE 1880 W.H. FROST EXPLAINED INTERPLAY OF FACTORS CAUSING EPIDEMICS 1889 WILLIAM FARR ANALYSIS OF VITAL STATISTICS & EFFECTS OF IMPRISONMENT IN PRISONERS 1849 JOHN SNOW NATURAL EXPERIMENT ON LONDON CHOLERA 1881 FINLAY MOSQUITO BORNE NATURE OF YELLOW FEVER 1900 BRADFORD HILL .A CONCEPT OF RANDOMIZATION & SMOKING AND LUNG CANCER EXPERIMENTS. GROWTH FROM 17 TH -19 TH CENTURY

4. Historical development Hippocrates 400BC he explained disease occurrence from a rational rather than a supernatural viewpoint He wrote an essay titled “ On Airs, Waters, and Places” Environmental and host factors might influence the development of disease.

5. Historical development contd. Hippocrates contd. He advised that factors causing disease be searched Air (hot &cold winds) Water (marshy, soft, hard, from rocky soil, unfit for cooking) Places (naked without vegetation, deficient in water, well watered, elevated and cold) Personal habits

6. Historical development contd. John Graunt ( 1600AD) A London tradesman and founding member of the Royal Society of London He became the first epidemiologist, statistician, and demographer Summarized the Bills of Mortality for his 1662 publication. This publication was the first to quantify patterns of birth, death, and disease occurrence, noting disparities between males and females, high infant mortality, urban/rural differences, and seasonal variations .

7. Historical development contd. John Graunt ( 1600AD) He counted the mortality rates for 37 years in London from the Bills of mortality and found . Constancy in the ratio from male to female in births and deaths. Age specific mortality is higher among males than in females. Seasonal fluctuations in deaths from various causes.

8. Historical development contd. John Graunt ( 1600AD) Measured the ebb and flow of various diseases and the host factors . Suggested quantitative methods to test the hypothesis of this variations.

9. Historical development contd. James Lind (1716- 1794) A Scottish Naval Surgeon, conducted a true experiment on his 12 soldiers suffering from Scurvy V inegar Mixture of nutmeg, garlic, mustard and tamarind in barley water Elixir vitrol Seawater Cider Two oranges and one lemon

10. Historical development contd. Edward Jenner (1796) Was an English Physician The first person to immunize against smallpox with cowpox vaccine His discovery paved way for preventive medicine and epidemiology.

11. Historical development contd. William Farr (1807-1883) He is considered one of the founders of modern epidemiology T he father of modern vital statistics and surveillance Farr was the compiler of Statistical Abstracts for the General Registry Office in Great Britain from 1839 through 1880. He analyzed the vital statistics for 40 years and made valuable observations with regard to the then health situation and recommended their application for public health improvement.

12. Historical development contd. William Farr (1807-1883) contd. He found high mortality in certain occupations like miners. He studied the health of prisoners and found that while 8 only died due to executions, 52 died of imprisonment. He also found that fluctuations in marriage rates depend upon price of bread, cholera, population movements and person’s monetary value.

13. Historical development contd. William Farr (1807-1883) contd. His findings paved the way for proper health planning and policies and thus fostered epidemiology and occupational health and safety .

14. Historical development contd. John Snow (1813-1858) He was a Physician for Queen Victoria and a a great epidemiologist He is considered the father of” field epidemiology” Controlled cholera in London He was able to prove his hypothesis by means of natural experiment that contaminated water is the vehicle for cholera spread.

15. Historical development contd. Fletcher (1905) Fletcher studied Beriberi that occurred in lunatics in mental asylum in Kuala Lumpur (Malaysia) and proved that it is due to nutritional deficiency. He used parboiled rice and Siamese rice for his true experiment.

16. Historical development contd. Goldberger Joseph (1915) He proved that Pellagra is not an infectious disease as it was thought earlier, but a nutritional deficiency state.

17. Historical development contd. Modern epidemiology In the 1930s and 40s epidemiologists extended their methods to non infectious diseases. The study of Richard Doll and Bradford Hill In 1980s epidemiologists extended the study to injuries and violence.

18. Historical development contd. Modern epidemiology contd. In 1990s it was extended to related of molecular and genetic epidemiology. Today, health workers throughout the world accept and use epidemiology, regularly to characterize the health of the communities and to solve day-day problems, large and small.

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