Introduction to Epidemiology

Epidemiology Introduction

• Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations.
• It also involves applying this study to the prevention and control of health problems.
• Epidemiologists are concerned with death, illness, disability, but also with positive health states and improving overall health.
• "Disease" encompasses unfavorable health changes including injuries and mental health.

Course Content

• Introduction to epidemiology
• Measuring health and disease
• Causation in epidemiology
• Epidemiology and prevention of chronic non-communicable diseases
• Communicable diseases (surveillance and response)
• Clinical epidemiology
• Environmental and occupational epidemiology.
• Epidemiology, health policy, and planning.

What is Epidemiology?

• Its origins date back to Hippocrates (more than 2000 years ago), initially through observing the influence of environmental factors on disease occurrence.
• In the 19th century, the measurement of disease distribution in specific population groups began.
• John Snow's finding linking cholera risk in London to a specific water company is a key example of early epidemiological work.

Definition of Epidemiology

• The study of the distribution and determinants of health states and events in specific populations, and also ways to prevent and control health problems.

Scope of Epidemiological Study

• Epidemiological studies focus on populations defined geographically or by other characteristics (hospital patients or factory workers, for example).

Early Studies

• Early studies in epidemiology focused on understanding the causes (etiology) of communicable diseases.
• This work is essential for identifying preventive methods and improving population health, especially that of the disadvantaged.

Causation of Disease

• While some diseases arise solely from genetic factors, most are caused by interactions between genetic and environmental factors (e.g., diabetes).
• Personal behaviors play a role in this interplay.
• Epidemiology studies the influence of these behaviors and the effects of preventive interventions.

Natural History of Disease

• The natural history of disease outlines the typical progression from good health, to subclinical changes, then clinical disease, and ultimately to death or recovery.

Health Status of Populations

• Epidemiology describes the health status of population groups to assess disease burdens.
• This information helps health authorities prioritize health programs to maximize limited resources, especially in prevention and treatment.
• This includes certain areas such as environmental and occupational epidemiology.

Achievements in Epidemiology: Smallpox

• The elimination of smallpox greatly improved the health of millions, especially the impoverished.
• The 1790s showed cowpox protection against smallpox, but widespread adoption took almost 200 years.
• The World Health Organization (WHO) coordinated an intensive campaign for elimination.

Epidemiological Methods for Smallpox

• Smallpox had distinct characteristics important for eradication:
  • No non-human hosts
  • No subclinical carriers
  • Immunity in recovered individuals
  • Not as rapidly spreading as other infectious diseases
  • Primarily spread through human-to-human contact
  • Bedridden patients when infectious, which limited transmission. This made eradication possible.

Successful Smallpox Eradication

• A ten-year eradication program (WHO, 1967) involved 10-15 million new cases and 2 million deaths annually in 31 countries.
• By 1976, cases were reported in limited countries.
• The final naturally occurring case was in 1977; smallpox was declared eradicated on May 8, 1980.

Contributing Factors to Smallpox Eradication

• Universal political commitment
• Well-defined goals and timetables
• Well-trained personnel
• A flexible strategy
• Development of an effective heat-stable vaccine (stockpile)