Applied Sciences

Introduction to Epidemiology

David Celentano, ScD, MHS Johns Hopkins University

JHU Vision of Epidemiology

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The material in this video is subject to the copyright of the owners of the material and is being provided for educational purposes under rules of fair use for registered students in this course only. No additional copies of the copyrighted work may be made or distributed.

What Is Epidemiology?

 The study of how disease is distributed in populations and what factors influence or determine this distribution

Epidemiology

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 The study of the distribution and determinants of health and disease in human populations to enable:  Health services to be planned rationally  Disease surveillance to be carried out  Preventive and control programs to be implemented and evaluated

Epidemiology

5Source: World Health Organization

 Epidemiology denotes the design, conduct, and analysis of studies in human populations designed to answer valid biologic questions that are of public health and clinical significance

Epidemiology

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 Epidemiologic illusions

 Don’t be fooled!

Why Do We Need Epidemiology?

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Does MMR Vaccine Cause Autism?

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Epidemiology and Public Health

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 Assess the burden of disease

 Assess risk factors for disease

 Evaluate interventions

 Make policy

 Communicate with the public

Public Health Activities

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 Tools to:  Measure disease burden  Assess risk factors for disease  Evaluate interventions  Assist policy decisions  Communicate public health evidence

Epidemiological Tool Box

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Tools to measure disease burden

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Changes in the Leading Causes of Death: United States

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Outbreaks

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Changes in Counts over Time

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Cases and Rates

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Spatial Distribution of Rates

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William Farr and Epidemic Models: Fit Mathematical Curves to Counts of Disease to Predict Future Patterns

The material in this video is subject to the copyright of the owners of the material and is being provided for educational purposes under rules of fair use for registered students in this course only. No additional copies of the copyrighted work may be made or distributed.

Tools to Measure Risk Factors

Section B

1. To study the factors associated with increased risk

Why Do We Try to Identify Groups at High Risk for Disease?

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1. To study the factors associated with increased risk

2. To direct preventive efforts and screening programs for early detection to appropriate populations

Why Do We Try to Identify Groups at High Risk for Disease?

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What Are the Risk Factors for Gonorrhea in Multnomah County?

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Counts Stratified by Sex

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Counts Stratified by Age

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 Determine whether there is or is not an association between a factor or characteristic and the development of a disease:  By studying the characteristics of groups  By studying the characteristics of individuals

Epidemiological Reasoning: Step 1

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 Derive appropriate inferences regarding a possible causal relationship from the patterns of association which have been found

 Look out for those epidemiologic illusions (confounding)

Epidemiological Reasoning: Step 2

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 Measures of risk  Odds ratio  Relative risk

2 x 2 Tables and Measures of Risk

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Disease Nodisease

Exposure a b

No exposure c d

The material in this video is subject to the copyright of the owners of the material and is being provided for educational purposes under rules of fair use for registered students in this course only. No additional copies of the copyrighted work may be made or distributed.

Tools to Evaluate Interventions

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Natural History of Disease

► Porta definition: “the course of a disease from pathological onset or inception to resolution”

Source: Porta, M. A dictionary of epidemiology.

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Natural History of Disease: General Model

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Natural History of Cervical Cancer

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Three Types of Prevention—1

Type of prevention Definition Examples

Primary Preventing the initial developmentof a disease

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Three Types of Prevention—2

Type of prevention Definition Examples

Primary Preventing the initial developmentof a disease Immunization, reducing exposure to a risk factor

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Three Types of Prevention—3

Type of prevention Definition Examples

Primary Preventing the initial developmentof a disease Immunization, reducing exposure to a risk factor

Secondary Early detection of existing diseaseto reduce severity, complications

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Three Types of Prevention—4

Type of prevention Definition Examples

Primary Preventing the initial developmentof a disease Immunization, reducing exposure to a risk factor

Secondary Early detection of existing diseaseto reduce severity, complications Screening for cancer

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Three Types of Prevention—5

Type of prevention Definition Examples

Primary Preventing the initial developmentof a disease Immunization, reducing exposure to a risk factor

Secondary Early detection of existing diseaseto reduce severity, complications Screening for cancer

Tertiary Reducing the impact of the disease

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Three Types of Prevention—6

Type of prevention Definition Examples

Primary Preventing the initial developmentof a disease Immunization, reducing exposure to a risk factor

Secondary Early detection of existing diseaseto reduce severity, complications Screening for cancer

Tertiary Reducing the impact of the disease Rehabilitation for stroke

The material in this video is subject to the copyright of the owners of the material and is being provided for educational purposes under rules of fair use for registered students in this course only. No additional copies of the copyrighted work may be made or distributed.

Jenner on Smallpox and Snow on Cholera

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Edward Jenner and Vaccination against Smallpox

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John Snow and the Broad Street Pump

Photo originally uploaded by Rsabbatini. Creative Commons BY 4.0. Accessed December 17, 2018, at Wikipedia. Map is in the public domain. Accessed December 17, 2018, at Wikimedia Commons.

https://en.wikipedia.org/wiki/John_Snow#/media/File:John_Snow.jpg
https://commons.wikimedia.org/w/index.php?title=Special:Search&limit=20&offset=20&ns0=1&ns6=1&ns12=1&ns14=1&ns100=1&ns106=1&search=broad+street+pump+map&advancedSearch-current=%7B%22namespaces%22:%5B6,12,14,100,106,0%5D%7D#/media/File:Snow-cholera-map.jpg
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Deaths from Cholera per 10,000 Houses, by Source of Water Supply, London, 1854

Water supply Number of houses Deaths from cholera Deaths per 10,000 houses

Southwark and Vauxhall Co. 40,046 1,263 315

Lambeth Co. 26,107 98 37

Other districts in London 256,423 1,422 59

Source: Snow. (1936).

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Cholera: Broad Street Pump Epidemic Investigated by Snow

The material in this video is subject to the copyright of the owners of the material and is being provided for educational purposes under rules of fair use for registered students in this course only. No additional copies of the copyrighted work may be made or distributed.

Tools to Assist Policy Decisions

Leading and Actual Causes of Death

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Weighing Risks and Benefits: Poliomyelitis in the United States, 1980–2005

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0

2 4

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10 12

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1980 1984 1988 1992 1996 2000 2004

C as

es

VAPP Imported

Tools to communicate public health evidence

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Public Health Messages

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What Is the Message?

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 Learning the epidemiological tools of public health allows one to: 1. Measure disease burden 2. Assess risk factors for disease 3. Evaluate interventions 4. Provide the evidence base for policy decisions 5. Communicate public health evidence

Summary

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a
Introduction to Epidemiology
JHU Vision of Epidemiology
Slide Number 3
Epidemiology
Epidemiology
Epidemiology
Why Do We Need Epidemiology?
Slide Number 8
Slide Number 9
Does MMR Vaccine Cause Autism?
Epidemiology and Public Health
Public Health Activities
Epidemiological Tool Box
Tools to measure disease burden
Changes in the Leading Causes of Death: United States
Outbreaks
Changes in Counts over Time
Cases and Rates
Spatial Distribution of Rates
William Farr and Epidemic Models: Fit Mathematical Curves to Counts of Disease to Predict Future Patterns
b
Section B
Why Do We Try to Identify Groups at High Risk for Disease?
Why Do We Try to Identify Groups at High Risk for Disease?
What Are the Risk Factors for Gonorrhea in Multnomah County?
Counts Stratified by Sex
Counts Stratified by Age
Epidemiological Reasoning: Step 1
Epidemiological Reasoning: Step 2
2 x 2 Tables and Measures of Risk
c
Tools to Evaluate Interventions
Natural History of Disease
Natural History of Disease: General Model
Natural History of Cervical Cancer
Three Types of Prevention—1
Three Types of Prevention—2
Three Types of Prevention—3
Three Types of Prevention—4
Three Types of Prevention—5
Three Types of Prevention—6
d
Jenner on Smallpox and Snow on Cholera
Edward Jenner and Vaccination against Smallpox
John Snow and the Broad Street Pump
Deaths from Cholera per 10,000 Houses, by Source of Water Supply, London, 1854
Cholera: Broad Street Pump Epidemic Investigated by Snow
e
Slide Number 1
Leading and Actual Causes of Death
Weighing Risks and Benefits: Poliomyelitis in the United States, 1980–2005
Tools to communicate public health evidence
Public Health Messages
What Is the Message?
Summary
Slide Number 8

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