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    The History and Scope of Epidemiology

    The History and Scope of Epidemiology

    Epidemiology PubH4040

    1/9/2018 11: History & Scope

    Learning Objectives

    • Define the term epidemiology

    • Define the components of epidemiology (determinants, distribution, morbidity, and mortality)

    • Name and describe characteristics of the epidemiologic approach

    • Discuss the importance of Hippocrates’ hypothesis and how it differed from the common beliefs of the time

    • Discuss Graunt’s contributions to biostatistics and how they affected modern epidemiology

    • Explain what is meant by the term natural experiments, and give at least one example

    1/9/2018 21: History & Scope

    Infectious and Chronic Disease • Hepatitis A outbreak – Utah

    – https://www.ksl.com/?sid=46232231&nid=148

    • –

    1/9/2018 1: History & Scope 3

    Utah Opioid Drug Deaths • In 2014, 32% of adults were prescribed an opiod pain

    reliever

    • 23 individuals die in Utah each month to overdose

    – Outpaces deaths due to firearms, falls, and motor

    vehicles

    – Utah ranks 7th in the U.S. for drug poisoning deaths

    1/9/2018 1: History & Scope 4

    Epidemiology is more than

    infectious and chronic diseases

    Epidemiology is more than

    infectious and chronic diseases

    Epidemiology Defined

    • Epidemiology derives from “epidemic,”

    originating from the Greek words

    – epi – prefix meaning on, upon, or befall

    – demos – root meaning the people

    – logos – suffix meaning the study

    • In other words, epidemiology is the study

    of what befalls the population

    1/9/2018 71: History & Scope

    Definition of Epidemiology

    • Epidemiology is concerned with the

    distribution and determinants of health and

    diseases, morbidity, injuries, disability, and

    mortality in populations.

    • Epidemiologic studies are applied to the

    control of health problems in populations.

    1/9/2018 81: History & Scope

    Determinants

    • Factors or events that are capable of

    bringing about a change in health.

    • Search for causes and other factors of

    health-related states or events.

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    Examples of Determinants

    • Health-related states or events

    • Disease states

    • Biologic agents – bacteria, virus, fungus

    • Chemical agents – carcinogens

    • Conditions associated with health

    • Physical activity or high-fat diet

    • Nutrition

    • Environmental poisoning

    • Seat belt use

    • Provision and use of health services

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    The Search for Determinants

    • Numerous examples in textbook

    – 1970s Love Canal – Hooker chemical

    and Niagara Fall, NY

    – 1980 Red Spots on Eastern Airline

    Flight Attendants–dye from life vests

    – 1993 Hantavirus outbreak

    • 4 corners (Utah)

    – 2001 Anthrax outbreak

    • Bioterrorism

    1/9/2018 111: History & Scope

    Bioterrorism-Associated Anthrax

    Cases • Index case reported in

    Florida.

    • Additional cases,

    including fatal cases,

    reported in New York,

    New Jersey, Connecticut.

    • Contaminated mail linked

    to some of the cases.

    1/9/2018 121: History & Scope

    Distribution

    • Study of frequency and pattern of health

    events in the population

    • Frequency – number, and number in

    relation to the population

    • Pattern – the health-related state or event

    by person, place, and time characteristics

    1/9/2018 131: History & Scope

    Disease Distribution Examples

    • CHD death rates and stroke were higher

    among African-Americans than among

    American Indian/Alaskan natives,

    Asian/Pacific Islanders, or whites – What are the underlying factors?

    • HIV rates in Utah from 2000-2010 are 40

    times higher in African-born immigrants

    living in Utah than Utah Caucasian males – Even though there are more cases in Caucasian-males

    1/9/2018 141: History & Scope

    Population

    • Epidemiology examines disease

    occurrence among population groups,

    not individuals.

    – TSS increase in the 1980’s

    • Epidemiology is often referred to as

    population medicine.

    • The epidemiologic description indicates

    variation by age groups, time,

    geographic location, and other variables.

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    Health Phenomena

    • Epidemiology investigates many

    different kinds of health outcomes:

    – Infectious diseases

    – Chronic diseases

    – Disability, injury, limitation of activity

    – Mortality

    – Active life expectancy

    – Mental illness, suicide, drug addiction

    1/9/2018 161: History & Scope

    Morbidity and Mortality

    • Morbidity–designates illness.

    • Mortality–refers to deaths that occur in a

    population or other group.

    • Note that most measures of morbidity and

    mortality are defined for specific types of

    morbidity or causes of death.

    – What do we do with this data?

    1/9/2018 171: History & Scope

    Aims and Levels

    • To describe the health status of

    populations.

    • To explain the etiology of disease.

    • To predict the occurrence of disease.

    • To control the occurrence of disease.

    – Intervention or Prevention

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    Epidemiology Is Interdisciplinary

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    Foundations of Epidemiology • Interdisciplinary

    – Infant botulism

    • Methods and procedures

    – Quantification

    – Qualitative, demographic data – See next slide

    • Use of special vocabulary

    – Epidemic, pandemic, attack rate

    1/9/2018 201: History & Scope

    Quantification

    • Quantification is a central activity of

    epidemiology.

    • Epidemiologic measures often require

    counting the number of cases of disease.

    • Disease distributions are examined

    according to demographic variables such

    as age, sex, and race.

    – Also qualitative data

    1/9/2018 211: History & Scope

    Methods of quantification

    • Leading cause of

    mortality

    • 1900 compared to

    2009

    1/9/2018 1: History & Scope 22

    1/9/2018 1: History & Scope 23

    Epidemic frequency of disease • What is an epidemic….endemic?

    • How is this determined?

    1/9/2018 1: History & Scope 24

    1/9/2018 25 https://www.cdc.gov/flu/weekly/usmap.htm

    – Current data

    suggests that 2017-18

    vaccine is

    approximately 39%

    effective

    Infectious Disease Epidemics

    • A single case of a long absent

    communicable disease.

    • First invasion of a communicable

    disease.

    • Two cases of such a disease associated

    in time and place are

    sufficient evidence of

    transmission to be

    considered an epidemic. 1/9/2018 261: History & Scope

    1/9/2018 1: History & Scope 27

    Infectious disease triangle

    1/9/2018 1: History & Scope 28

    Pandemic • “ . . . an epidemic on a worldwide scale; during a pandemic, large

    numbers of persons may be affected and a disease may cross

    international borders.” An example is a flu pandemic.

    291: History & Scope

    Concept of Epidemic and Non-

    Infectious Diseases

    • Some examples that use the concept of an

    epidemic are:

    – Love Canal

    – Asbestosis among shipyard workers

    – Diseases associated with lifestyle

    1/9/2018 301: History & Scope

    Ascertainment of Epidemics

    • Surveillance

    – The systematic collection of data pertaining to

    the occurrence of specific diseases.

    – Analysis and interpretation of these data.

    – Dissemination of disease-related information.

    1/9/2018 311: History & Scope

    1/9/2018 1: History & Scope 32

    1/9/2018 1: History & Scope 33

    Ascertainment of Epidemics

    • Epidemic Threshold

    – The minimum number of cases (or deaths)

    that would support the conclusion that an

    epidemic was underway.

    • Are 10 obese individuals in this classroom

    an epidemic?

    • Is one case of human anthrax infection an

    epidemic?

    1/9/2018 341: History & Scope

    Historical Epidemiological Antecedents

    • Environment and disease

    • The Black Death

    • Use of mortality counts

    • Smallpox vaccination

    • Use of natural experiments

    • Identification of specific agents of disease

    • The 1918 influenza pandemic

    1/9/2018 351: History & Scope

    The Environment

    • Hippocrates wrote On Airs, Waters, and

    Places in 400 BC.

    • Father of medicine and first epidemiologist

    • He suggested that disease might be

    associated with the physical environment. – Malaria and swampy water

    • Represented a movement

    away from supernatural

    explanations of disease

    causation.

    1/9/2018 361: History & Scope

    The Black Death • Occurred between 1346-1352

    • Claimed one-quarter to one-third of

    population of Europe

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    1/9/2018 1: History & Scope 38

    Use of Mortality Counts

    • John Graunt, in 1662, published Natural

    and Political Observations Made upon the

    Bills of Mortality. – Recorded how many persons per year died of what

    kind of event or disease

    – Developed and calculated life tables and life

    expectancy

    – Divided deaths into two types of causes

    • Acute (struck suddenly – e.g., cholera)

    • Chronic (lasted over a long period of time – e.g.,

    emphysema) 1/9/2018 391: History & Scope

    Edward Jenner

    • Jenner attempted to give a

    dairymaid, exposed to a mild

    case of cowpox in her youth, a

    case of cowpox by cutting her

    arm and rubbing some of the

    infectious “grease” into the

    wound. She did not get ill.

    • He subsequently invented a

    vaccination for smallpox

    1/9/2018 401: History & Scope

    Use of Natural Experiments

    • John Snow was an

    English physician and

    anesthesiologist.

    • He investigated a

    cholera outbreak that

    occurred during the

    mid-19th century in

    Broad Street, Golden

    Square, London.

    1/9/2018 411: History & Scope

    Snow’s Contributions

    • Linked the cholera epidemic

    to contaminated water

    supplies.

    • Used a spot map of cases

    and tabulation of fatal

    attacks and deaths.

    1/9/2018 421: History & Scope

    Snow’s Natural Experiment

    • Two different water companies supplied water from the Thames River to houses in the same area.

    • The Lambeth Company moved its source of water to a less polluted portion of the river.

    • Snow noted that during the next cholera outbreak those served by the Lambeth Company had fewer cases of cholera.

    1/9/2018 431: History & Scope

    • Black lines

    represent case

    of cholera

    1/9/2018 44

    1/9/2018 1: History & Scope 45

    Natural Experiment

    • Definition: The epidemiologist does not

    manipulate a risk factor but rather

    observes the changes in an outcome as

    the result of a naturally occurring

    situation.

    • Contemporary Natural Experiments

    – Currently, natural experiments may be the

    result of legislation, policy changes or

    environmental interventions.

    1/9/2018 461: History & Scope

    Examples of Contemporary

    Natural Experiments

    • Seat Belt Law–Did seat belt use reduce

    fatalities from motor vehicle accidents?

    • Tobacco Tax–Did the increase in cigarette

    price decrease the sale of cigarettes?

    1/9/2018 471: History & Scope

    Ignaz Semmelweis • Mid 1800’s

    • Described as the “savior of mothers”

    • Early pioneer of antiseptic procedures

    • Proved that childbed fever resulted from physicians not washing their hands after dissections

    • Could not “prove” and many disregarded recommendation until Louis Pasteur and germ theory

    William Farr

    • Appointed compiler of abstracts in

    England, 1839.

    • Provided foundation for classification of

    diseases

    – International Classification of Disease system

    • Examined linkage between mortality rates

    and population density.

    – Healthier population districts

    1/9/2018 491: History & Scope

    Koch’s Postulates • Robert Koch – Established germ theory

    • Microorganism must be observed in every

    case of the disease.

    • Microorganism must be isolated and grown in

    pure culture.

    • Pure culture must, when inoculated into a

    susceptible animal, reproduce the disease.

    • Microorganism must be observed in, and

    recovered from, diseased animal.

    – Anthrax was transmissible

    1/9/2018 501: History & Scope

    The 1918 Influenza Pandemic • Occurred between 1918 and 1919

    • Killed 50- to 100 million persons

    worldwide

    • 2.5% case-fatality rate versus 0.1% for

    other influenza pandemics

    • Deaths most

    frequent among

    20- to 40-year-olds

    – How is that different

    than today? 1/9/2018 511: History & Scope

    Recent Applications of

    Epidemiology

    • Framingham Heart Study (since 1948)

    – Investigates coronary heart disease risk

    factors.

    • Smoking and lung cancer; e.g., Doll and

    Peto’s study of British doctors’ smoking.

    • AIDS, chemical spills, breast cancer

    screening, secondhand smoke.

    1/9/2018 521: History & Scope

    Additional Applications of

    Epidemiology • Infectious diseases

    – Avian influenza, H1N1, Listeria

    • Environmental health

    • Chronic diseases

    • Lifestyle and health promotion

    • Psychiatric and social epidemiology

    • Molecular and genetic epidemiology

    1/9/2018 531: History & Scope

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