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HSS4303B

What Is Epidemiology?

Introduction To Epidemiology

Science of the Gods

The Origin of Epidemiology

• “The study of the distribution and determinants of disease or health status in a population” – CDC

Dr John Snow 1854 Used non-medical means to discover source of cholera outbreak

• The Science of the Gods!

Introduction

– R. Deonandan

Prof R Deonandan – [email protected]

Epidemiology Allowed “Miasmatic Theory” to be Displaced

Shoe leather epidemiology

http://www.ph.ucla.edu/epi/snow/snowcricketarticle.html “Within 250 yards of the spot where Cambridge Street joins Broad Street there were upwards of 500 fatal attacks of cholera in 10 days,” Dr. Snow wrote “As soon as I became acquainted with the situation and extent of this irruption (sic) of cholera, I suspected some contamination of the water of the much-frequented streetpump in Broad Street.”

• Miasmatic theory

– Miasma was considered to be a poisonous vapor or mist filled with particles from decomposed matter (miasmata) that caused illnesses. It was identifiable by its foul smell. • Supplanted by “Germ theory”

– Most diseases caused by an infectious agent Figure 1-12 Photograph of John Snow. (From the Wellcome Historical Medical Museum and Library, London.)

Deaths from cholera and water theory

Figure 1-13 A drop of Thames water, as depicted by Punch in 1850. (From Extracts from Appendix (A) to the Report of the General Board of Health on the Epidemic Cholera of 1848 and 1849, published by HMSO, London, 1850. Int J Epidemiol 31:900-907, 2002.)

Types of Epidemiologists • Clinical Epidemiologist

Water supply

# of houses

Deaths from cholera

Deaths per 10,000 houses

Southwark and Vauxhall Co

40,046

1,263

315

Lambeth Co

26,107

98

38

Other districts in London

256,423

1,422

56

• Public Health Epidemiologist • Population Epidemiologist

The Face of Brilliance HSS4303: Introduction to epidemiology

Epidemiology In Pop Culture

Village of the Damned (1995)

Outbreak (1995)

Contagion (2011)

ReGenesis (2004)

Fringe (2009)

Dr Deonandan? I think not!

Paradigms of Research Different disciplines embrace different paradigms. All tend to be based on three philosophies: Ontology – inquiry into how we define and experience reality Epistemology – how we acquire and process knowledge Methodology – tools for identifying and categorizing knowledge

Paradigms of Research Purposes of a research paradigm... - Define how the world works, how knowledge is extracted from this world, and how one is to think, write, and talk about this knowledge - Define the types of questions to be asked and the methodologies to be used in answering those questions - Decide what is published and what is not published - Structure the world - Provide the world’s meaning and its significance

Paradigms of Research Epidemiology exists within the Etiologic paradigm, a type of Positivism, which purports to identify and quantify causal relationships between factors and a health outcome I bring this up because: -students and practitioners of Epidemiology often forget it is but one path to knowledge, and we should not be so fast to deride other paths.

Some Terminology • Clinical research or mathematical relationships:

– Variable that predicts/causes an outcome is independent variable • Epidemiological research:

– Variable that may predict/cause an outcome is exposure

Some Terminology

Some Terminology

• Traditionally: • Epidemiological research:

– Dependent variable

Independent variable

• In Epidemiology:

– Outcome

Exposure

Lung cancer

– Exposures that increase or decrease the likelihood of developing certain disorders, conditions or diseases are called risk factors

Smoking Eg, research has shown a strong statistical association between the exposure of smoking and the outcome of having lung cancer smoking is therefore a risk factor for lung cancer.

Qualitative vs. Quantitative

Descriptive Studies

Descriptive Study Descriptive vs. Analytic

• Who • A true “descriptive study” is an example of “descriptive epidemiology”

– Who – What – Where – When

– Students

Who gets the disease? When do they get it? Where do they get it?

• What

– Left handedness

Right now, 23% of students in this class are left handed

Observational vs. Experimental

Cross-sectional?

• Where

– This class • When

Case-control Cohort Cross-sectional

– Right now

Ecological studies?

RCTs (Clinical trials) Quasi-experiments Natural experiments

EXPERIMENTAL STUDY

What Is An Experiment? From the internet: “the act of conducting a controlled test or investigation”

For our purposes, an experiment differs from other kinds of investigations in that the researcher manipulates something.

Historical Triumphs of Epidemiology

“You have erased from the calendar of human afflictions one of its greatest. Yours is the comfortable reflection that mankind can never forget that you have lived. Future nations will know by history only that the loathsome smallpox has existed.”

Smallpox

– 400,000 people died each year in the late 18th century – 1/3 of the survivors became blind – Survivors also developed immunity to smallpox – Efforts to prevent smallpox

The global eradication of smallpox was certified, based on intense verification activities in countries, by a commission of eminent scientists on 9 December 1979 and subsequently endorsed by the World Health Assembly on 8 May 1980 -“Resolution WHA33.3”

-Thomas Jefferson to Edward Jenner, 1806 In 1975, two year old Rahima Banu contracted last known case of naturally-occurring variola major Smallpox. -Wikipedia

Global eradication was possible because of…

Online tutorial on herd immunity • http://www.health.harvard.edu/video/herd-immunity/

Herd immunity

• Variolation

– Edward Jenner took interest in cowpox to find solutions in the prevention of smallpox – WHO and eradication of smallpox • • • •

In 1967 WHO began the eradication program 15 million people developed smallpox annually 2 million people died In 1980 smallpox was “eradicated”

More Triumphs of Epidemiology

Before HIV was known to cause AIDS • We knew it involved the “3 H’s”

– Homosexuals – Haemophiliacs – Haitians • Epidemiologists figured out:

– It was bloodborne – It was probably a virus

Observational epidemiology • Many a times we do not know the cause of disease but we can associate it with certain exposures – Streptococcal infection follows rheumatic fever and rheumatic heart disease – Rheumatic fever is more frequent in army recruits than in school children

• Lung cancer and smoking • Epidemiology based on observational data leads us to understand the association between the morbidity and mortality from a disease and certain exposures, habits, lifestyle choices

Where Do Epidemiologists Work?

What Are Some Of The Things That Epidemiologists Do?

• Universities (ahem) • Government • Public health agencies • Drug companies • Hospitals (MDs) • Private companies

Some important tasks in epidemiology

Trend Analysis

• Disease surveillance • Diagnostic tests (sensitivity/specificity) • Trend analysis • Experimental design

Figure 1-14 Breast versus lung cancer mortality: white females versus black females, United States, 1973-1995, age-adjusted to 1970 standard. (From Ries LAG, Kosary CL, Hankey BF, Miller BA, Edwards BK [eds]: SEER Cancer Statistics Review, 1973-1995. Bethesda, MD, National Cancer Institute, 1998.)

Things I Want You to Think About • Consider the following three images and the reaction they have on you. We will discuss at a later date. • Consider: how do you respond to the numbers, do you think about who computed them and whether they are accurate, are they appropriate, and what emotional reaction do you have from them? It’s put out by the Canadian Foundation for AIDS Research (CANFAR) and says, “Did you know that 86% of HIV Positive Canadians are male, And 2/3 of boys, aged 15 to 19 are sexually active? You think your kids aren’t at risk? Think again.” This is your homework