• 24 AUG 18
    • 0

    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


    • 23 individuals die in Utah each month to overdose

    – Outpaces deaths due to firearms, falls, and motor


    – 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


    • 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.

    1/9/2018 91: History & Scope

    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

    1/9/2018 101: History & Scope

    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


    • 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


    • 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


    • 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.

    1/9/2018 151: History & Scope

    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


    • To explain the etiology of disease.

    • To predict the occurrence of disease.

    • To control the occurrence of disease.

    – Intervention or Prevention

    1/9/2018 181: History & Scope

    Epidemiology Is Interdisciplinary

    1/9/2018 191: History & Scope

    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 is a central activity of


    • 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


    • 1900 compared to


    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%


    Infectious Disease Epidemics

    • A single case of a long absent

    communicable disease.

    • First invasion of a communicable


    • 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


    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


    1/9/2018 361: History & Scope

    The Black Death • Occurred between 1346-1352

    • Claimed one-quarter to one-third of

    population of Europe

    1/9/2018 371: History & Scope

    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


    – 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


    • 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


    • 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


    • 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


    – 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


    • 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


    • Framingham Heart Study (since 1948)

    – Investigates coronary heart disease risk


    • 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

    "Get 15% discount on your first 3 orders with us"
    Use the following coupon

    Order Now
    Leave a reply →

Leave a reply

Cancel reply


"Get 15% discount on your first 3 orders with us"
Use the following coupon

Order Now

Hi there! Click one of our representatives below and we will get back to you as soon as possible.

Chat with us on WhatsApp