Chapter 1: History, Philosophy, and Uses of Epidemiology

Public health

prevent disease and promote health of populations

Epidemiology

Study of distribution and determinants of health related phenomena in human populations and the application of this study to control health problems

Morbidity

 illness due to a specific disease or health condition

Mortality

deaths from various causes

Epidemic

 increase in number of cases of a specific disease (typically in a year) that is above what is expected

example: 22 cases of legionellosis occurred within 3 weeks among residents of a particular neighborhood

Epidemic threshold

expected occurrence of the disease each year

Outbreak

sudden rise in number of cases of a disease (above expected threshold), typically limited in geographic location/community

Infectious/communicable disease

disease caused by an infectious agent

Noninfectious/noncommunicable disease

disease is not caused by an infectious agent

Endemic

disease exists in a steady rates in a population

example: About 60 cases of gonorrhea are usually reported in this region per week, slightly less than the national average

Sporadic

disease occurs infrequently and irregularly

example: Single case of histoplasmosis is diagnosed in a community

Pandemic

epidemic on global scale

example: 1.1 million people died worldwide from influenza A

Surveillance

systematic and ongoing collection of data pertaining to specific disease → analyze/interpret data to draw conclusions, then disseminate disease related information

Epidemic threshold

critical number(minimum number)/density (number of cases or deaths) to designate an epidemic is occurring

Edward Jenner

First vaccine - small pox (late 1700s)

John Snow

Earliest example of social epidemiology

Examined water pumps as source of cholera infection in England (1854)

7 uses of epidemiology - #1

Study the history of the health of populations

• Health status and health services

• Examine trends of morbidity and mortality for a region

Factors that influence trends in mortality

• Aging population

• Changing lifestyles

• New medical tech/improvements to care

• changes to cultural values and public policy

• built environment

• diagnostic capabilities

Factors that influence morbidity

• changes in diagnostic criteria

• aging of population

• changes in disease fatality

Disappearing disorders

conditions were once common but are no longer present in epidemic form

accomplish via high availability and dissemination of vaccines + improving sanitary conditions

example = smallpox

Residual disorders

cause of disease is known but lack measures to control it

measure to control is often changing human behavior

example = tobacco use

Persisting disorders

Cause of disease is unknown, lack method of prevention/cure

example = mental health disorders

New epidemic disorders

diseases that are increasing in frequency, emergence of new epidemics

causes: increased life expectancy, new environmental exposures, changes in lifestyle

example = alzheimers

Population pyramid

represents age and sex composition of a country/area at a point in time

allows study of trends of past and prediction of future illness