CHAPTER 1: FOUNDATIONS OF EPIDEMIOLOGY

Objectives

• Define epidemiology

• Be familiar with the different elements of the definition

• Define risk factor and indicate why it does not mean cause

• Define epidemic, endemic, and pandemic

• Describe common-source, propagated, and mixed epidemics

• Describe why a standard case definition and adequate levels of reporting are important in epidemiologic investigations

• Describe disease transmission concepts

• Define the three levels of prevention used in public health and epidemiology

• Be familiar with the basic vocabulary used in epidemiology

• Explain the role of epidemiology in public health practice and individual decision-making

What is Health?

A holistic conception of health was adopted by the World Health Organization (WHO) in their 1948 definition of health, which is “a state of complete physical, mental, and social wellbeing, not merely the absence of infirmity or disease.”

What is Public Health?

• Public health is the science and art of promoting health and extending life on the population level

• Public health is concerned with threats to health in the population (a group of people sharing one or more characteristics)

• The mission of public health is to ensure conditions that promote the six dimensions of health (physical, emotional, intellectual, social, environmental, and social) in the population

What is the Meaning of Population?

• Population refers to a collection of individuals that share one or more observable personal or observational characteristics from which data may be collected and evaluated

  • Social

  • Economic

  • Family (marriage and divorce)

  • Work and labor force

  • Geographic factors

How does Public Health Relate to Epidemiology?

• Epidemiology focuses on individuals who share one or more observable characteristics (e.g., a social group, an income level, a type of worker, or where they live) from which data are collected, analyzed, and interpreted

• Epidemiologic data support objectives or preventing disease, disability, and death and promoting well-being (a state of health, happiness, or prosperity)

• Hence, epidemiology may be thought of as the foundation of public health

What is Epidemiology?

• Epidemiology is the study of the distribution and determinants of health-related states or events in human populations, and the application of this study to prevent and control health problems

Distribution

• Refers to frequency and pattern

  • Frequency — the number of health-related states or events and their relationship with the size of the population

  • Pattern — a description of the health-related state or event described by:

    • Person - who?

    • Place - where?

    • Time - when?

    • Clinical criteria - what?

Determinants

• Factors that produce (cause) a health outcomes

• The emphasis on causality (the relating of causes to the effects they produce) in epidemiology is critical to effective prevention and corrective measures (interventions) for specific situations

• Identifying causal associations requires making a “judgement” based on the totality of evidence

Health-Related States or Events

• Disease states

  • Cholera, influenza, pneumonia, mental illness

• Conditions associated with health

  • Physical activity, nutrition, environmental poisoning, seat belt use, and provision and sue of health services

• Events

  • Injury, drug abuse, and suicide

Prevention and Control

• Prevention involves measures to avoid the occurrence of disease. Public health aims to prevent disease through population-based risk reduction interventions

• Control aims to prevent further spread of a disease in areas where an outbreak currently exists