Public Health Fundamentals and Epidemiology Concepts

Posted on Jul 23, 2025 in Other university degrees and diplomas

What is Public Health?

Public health is defined as “what we do as a society to collectively assure the conditions in which people can be healthy.”

Ten Public Health Achievements

  • Immunizations
  • Motor vehicle safety
  • Workplace safety
  • Control of infectious diseases
  • Declines in deaths from heart disease and stroke
  • Safer and healthier foods
  • Healthier mothers and babies
  • Family Planning
  • Fluoridation of drinking water
  • Reduction in tobacco use

Emerging Public Health Threats

  • Climate change and environmental hazards
  • Emerging infectious diseases (e.g., COVID-19, Zika)
  • Antimicrobial resistance
  • Mental health and substance use disorders
  • Chronic diseases (e.g., diabetes, heart disease)
  • Vaccine hesitancy and misinformation
  • Social determinants of health disparities

Purpose of Public Health

The goal of public health is to prevent disease, promote health, and prolong life at the population level by implementing policies, education, and interventions.

Public Health vs. Medicine

Public health focuses on populations, prevention, and interdisciplinary approaches, including politics, while medicine focuses on individuals, diagnosis, treatment, and health sciences.

Core Public Health Functions

  • Assessment: Identify trends in illness, injury, and death.
  • Policy Development: Information gathered under assessment is used to develop policies and programs.
  • Assurance: Focuses on making sure needed health services are available, maintaining the capacity of public health agencies, and constantly improving public health functions.

Essential Public Health Services

Assessment

  • Assess and monitor population health.
  • Investigate, diagnose, and address health hazards and root causes.

Policy Development

  • Communicate effectively to inform and educate.
  • Strengthen, support, and mobilize communities and partnerships.
  • Create, champion, and implement policies, plans, and laws.
  • Utilize legal and regulatory actions.

Assurance

  • Build a diverse and skilled workforce.
  • Improve and innovate through evaluation, research, and quality improvement.
  • Build and maintain a strong organizational infrastructure for public health.

The Role of Politics in Public Health

Political decisions are necessary before any action can be taken. Federal or state governments can challenge or block proposed public health actions.

Levels of Prevention

  • Primary: Prevent disease and harm before they occur (e.g., vaccination).
  • Secondary: Screening and early detection.
  • Tertiary: Treatment, rehabilitation, and healthcare management.

Market Justice vs. Social Justice

  • Market Justice: Individual responsibility, minimal government intervention, health seen as a personal choice.
  • Social Justice: Collective responsibility, government involvement, ensuring health equity.

Challenges to Public Health Initiatives

  • Economic Impact: Public health policies can be costly (e.g., smoking bans affecting the tobacco industry).
  • Individual Liberty: Policies like vaccine mandates or quarantine orders raise ethical questions about freedom.
  • Moral/Religious Opposition: Issues like contraception, abortion, or needle exchange programs can cause debate.

Historical Public Health Efforts

  • Early Contributions: Greeks (hygiene, fitness), Romans (sanitation, water systems).
  • Middle Ages: Quarantine, isolation.
  • Enlightenment: Harvey (circulation), Jenner (vaccination).
  • Great Sanitary Awakening (1800s–1900s): Birth of modern public health.

Government Branches & Public Health Law

  • Legislative: Passes bills like the Affordable Care Act (a health law).
  • Executive: Carries out laws and issues regulations (e.g., creating systems for ACA sign-ups).
  • Judicial: Public health regulations and laws can be challenged in court.

Public Health Agencies: Federal, State, Local

  • Local: County health departments, responsible for core public health functions, providing medical care for the poor, and day-to-day public health tasks.
  • State: Coordinate and fund local health agencies, collect and analyze data, provide laboratory services, manage Medicaid, license and certify, handle environmental issues, mental health issues, social services, and aging issues, and provide funding to hospitals.
  • Federal: CDC, NIH, FDA set policies, provide funding, and conduct research.

Understanding Epidemiology

  • Etymology: Three Greek Words: Epi = on/upon, Demos = people, Logos = the study of.
  • Definition: The study of the distribution and determinants of health-related states and events in populations, and the application of this study to control health problems.

Prevalence in Epidemiology

  • Definition: Proportion of a population that currently has the outcome.
  • Formula: Number of existing cases of disease / number in total population.
  • Types: Point (single point in time), Period (over a period).

Incidence in Epidemiology

  • Definition: Frequency at which new cases occur among the currently healthy subgroup.
  • Involves prospective monitoring.
  • Formula: Number of new cases of disease / population at risk at start of period (or total population – people at risk).
  • Also known as risk.

Descriptive Epidemiology: Person, Place, Time

  • Focus: Distribution, interested in who is sick, where the disease is occurring, and the patterns.
  • Person: Demographic, intrinsic, behavior/lifestyle factors.
  • Place: Geographic variations that influence health (climate, urban/rural).
  • Time: When are the events happening?

Descriptive vs. Analytic Epidemiology

  • Descriptive: Person, place, and time (Who was affected, where was the population affected, when was the population affected).
  • Analytic: The why and how; the goal is to estimate the association between the exposure and occurrence of a health outcome.

Understanding the 2×2 Table

  • A: Exposed with disease
  • B: Exposed without the disease
  • C: Unexposed with disease
  • D: Unexposed without disease

Types of Epidemiological Studies

  • Intervention (Experimental): Tests treatments (e.g., clinical trials).
  • Cohort: Observes exposure over time (e.g., smoking & lung cancer).
  • Case-Control: Compares those with/without disease (retrospective).
  • Cross-Sectional: Snapshot at one point in time.

Risk Ratio (RR)

  • Formula: RR = Re/Ru
  • Interpretation:
    • RR = 1: No association.
    • RR > 1: Increased risk.
    • RR < 1: Protective effect.

Odds Ratio (OR) for Case-Control Studies

Formula: OR = (A × D) / (B × C)

Errors and Biases in Research

  • Random Error: Sample issues (chance-based).
  • Bias: Systematic errors in study design.
    • Selection Bias: Unequal participant selection.
    • Information Bias: Misclassification (e.g., recall/interviewer bias).
  • Confounding: A third variable distorts the true association.

Association vs. Causation

  • Association: Two variables are linked.
  • Causation: One directly affects the other.

Why Statistics Matter in Public Health

  • Health trends
  • Risk analysis
  • Policy guidance

Key Public Health & Epidemiology Terms

  • p-Value: <0.05 suggests statistical significance.
  • Confidence Interval (CI): Estimated range for the true value.
  • Screening: Early disease detection.
  • Study Power: The ability to detect true effects.
  • Cost-Benefit Analysis: Weighs intervention effectiveness against its costs.

Prevention Levels & Screening Strategies

  • Primary: Prevent (e.g., vaccines).
  • Secondary: Detect early (e.g., mammograms).
  • Tertiary: Manage (e.g., rehabilitation).

Sensitivity vs. Specificity

  • Sensitivity: True positives.
  • Specificity: True negatives.

Public Health Rates & Calculations

  • Rate Formula: Cases/population × 100,000.
  • Crude vs. Adjusted Rates:
    • Crude: Basic calculations.
    • Adjusted: Accounts for demographics (e.g., age).

Risk Assessment vs. Risk Perception

  • Assessment: Data-based probability.
  • Perception: Public interpretation (often inaccurate).