Introduction to Epidemiology

Jul 4, 2024

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Introduction to Epidemiology 🍎

Instructor

  • Dr. Kate Glyn
  • Associate Director for Science at CDC's Division of Scientific Education and Professional Development

Course Overview

  • Definition and role of epidemiology
  • Characterizing public health problems
  • Steps in disease outbreak investigation

Objectives

  • Define epidemiology
  • Understand basic terminology and concepts
  • Identify data sources and methods of data collection
  • Describe public health problems by time, place, and person
  • Identify key components of a descriptive epidemiology outbreak investigation

Public Health Approach

  • Identify the problem through surveillance systems
  • Determine the cause (risk factors, environmental factors, behaviors)
  • Identify effective interventions
  • Implement the intervention considering resources and the affected population

Core Sciences in Public Health

  • Public Health Surveillance: Monitor health events/behaviors
  • Epidemiology: Study disease origin, movement, and prevention
  • Public Health Laboratories: Diagnose conditions, support research
  • Public Health Informatics: Efficient collection and use of electronic data
  • Prevention Effectiveness: Provide economic info for decision-making

Epidemiology

Definition

  • Study of the distribution and determinants of health-related states in populations
  • Application of this study to control health problems

Purpose

  • Discover agent, host, and environmental factors affecting health
  • Determine causes of illness, disability, death
  • Identify high-risk population segments
  • Evaluate health programs effectiveness

Public Health Approach Steps

  1. Data Collection: Public health surveillance (time, place, and person)
  2. Initial Conclusions: Based on collected data
  3. Hypothesis Generation: Causes of the public health problem
  4. Hypothesis Testing: Analytic epidemiology, tests/studies to determine how and why
  5. Intervention: Recommend and implement population-level actions

Key Terminology

  • Epidemic/Outbreak: Excess disease occurrence in a population
  • Cluster: Group of cases in a specific time/place
  • Endemic: Constant presence of disease in a population
  • Pandemic: Disease causing an epidemic spreading across regions
  • Rate: Number of cases in a specific period and population

Calculating Rates

  • Components: Number of cases, size of the population at risk, specific period
  • Formula: (Number of cases / Population at risk) * 100

Study Designs

Experimental Study

  • Investigator controls certain factors
  • Example: Vaccine efficacy trials

Observational Study

  • Investigator only observes
  • Types: Descriptive and Analytic

Descriptive Epidemiology

  • Collect and summarize data
  • Asks: When? Where? Who?

Analytic Epidemiology

  • Tests hypotheses
  • Asks: How? Why?

Data Sources and Collection Methods

  • Individuals: Questionnaires, surveys
  • Environmental: Samples, tests
  • Healthcare Providers: Clinical records
  • Non-health related: Financial, legal records

Common Study Designs

Cross-Sectional

  • Snapshot of the population at a point in time

Cohort

  • Follow a population over time
  • Categorizes based on exposure and follows health outcomes

Case-Control

  • Compares diseased (case patients) with non-diseased (control subjects)
  • Works backward to determine exposure/risk factors

Outbreak Investigation Steps

  1. Establish existence of an outbreak
  2. Prepare for fieldwork
  3. Verify the diagnosis
  4. Define and identify cases
  5. Use descriptive epidemiology
  6. Develop and evaluate hypotheses
  7. Refine hypotheses if needed
  8. Implement control and prevention measures
  9. Communicate findings

Example: Legionnaires' Disease in 1976

  • Unusual pneumonia cases among American Legion Convention attendees
  • Investigation included: case definition, data collection, hypothesis testing
  • Identified air conditioning system bacteria as the cause
  • Implemented measures for chlorination and cooling system regulations

Review

  • Epidemiology definition and terms
  • Steps and methods in public health practice
  • Importance of core sciences and their role in outbreak investigations

Additional Resources

  • Provided for further reading and information