1. Anita Sego
Spring, 2005

2. Chapter Objectives
Define the terms epidemic, epidemiology, and epidemiologist, and explain their importance in community health.
List some diseases that causes epidemics in the past and some that are causing epidemics today.
Discuss how the practice of epidemiology has changes since the days of Benjamin Rush and John Snow.

3. Chapter Objectives
Explain why rates are important in epidemiology and list some of the commonly used rates.
Define incidence and prevalence rates and provide and example of each
Calculate a variety of rates from the appropriate data.
Discuss the importance of disease reporting to a community’s health and describe the reporting process.

4. Chapter Objectives
Identify sources of standardized data used by epidemiologists, community health workers, and health officials and list the types of data available from each source.
Define the following standardized measurements of health status - life expectancy, years of potential life lost (YPLL), disability-adjusted life expectancy (DALEs).

5. Definitions Epidemiology Endemic Diseases Epidemic
is “the study of the distribution and determinants of diseases and injuries in human populations.” Mausner & Kramer, 1985
Endemic Diseases
a disease that occur regularly in a population
Epidemic
an unexpectedly large number of cases of disease in a particular population

6. Recent Epidemics in the United States
Disease Cases/Prev. yrs Period # of Cases
St. Louis ,815
encephalitis
Legionnaires’ Unknown
AIDS Unknown ,374
Lyme Disease Unknown ,000

7. Definitions Epidemiologist Epizootiologist Pandemic
one who practices epidemiology
Epizootiologist
one who studies disease outbreaks in animals
Pandemic
an outbreak of disease over a wide geographical area such as a continent
influenza pandemic of killed 25 million people worldwide

8. History of Epidemiology
300 B.C. - Hippocrates “Father of Medicine”
suggested a relationship between the occurrence of disease and the physical environment.
Yellow fever in Philadelphia
Killed 4,044 People
Cause discovered in 1901 by Walter Reed - Mosquito
Cholera in London
Dr. John Snow investigated
30 years before Pasteur “Germ Theory of disease”

9. Numbers and Rates Case Definition or “What” Rates Importance of Rates
a set of criteria for deciding whether a person has a particular disease or other health-related condition
Rates
the number of events that occur in a given population in a given period of time
Importance of Rates
allow for a comparison of outbreaks that occur at different times or in different places

10. 3 Important Kinds of Rates
# of live births to residents
in an area in a calendar year
Natality (birth) rate =
Population in the area
in the same year
# of cases of residents with illness
in an area in a calendar year
Morbidity (disease) rate =
Population in the area
in the same year
# of deaths to residents
in an area in a calendar year
Mortality (fatality) rate =
Population in the area
in the same year

11. 3 Important Types of Rates
# of new cases of a disease
in a certain time period
Incidence rate =
Population at risk
in same time period
# of new and old cases of a disease
in a certain time period
Prevalence rate =
Population at risk
in same time period
# of new cases in a narrowly defined population during a specific time period
Attack rate =
Population at risk
in same time period

12. Number of deaths (all causes)
Crude & Specific Rates
Number of deaths (all causes)
Crude death rate =
Estimated midyear population
Number of deaths
(35-44)
Age-specific death rate =
Estimated midyear
population (35-44)
Number of deaths
(specific cause)
Cause-specific death rate =
Estimated midyear
population

13. Reporting Births, Deaths, & Diseases
Doctors
Clinics
Hospitals
Centers for Disease
Control and
Prevention (CDC)
Local Health
Department
State Health
Department

14. Sources of Standardized Data
U.S. Census
conducted every 10 years, enumeration of population
Statistical Abstract of the U.S.
statistics on social, political, & economic organization
Vital Statistics
statistical summaries of records of major life events

15. Sources of Standardized Data
Morbidity & Mortality Weekly Reports (MMWR)
lists cases of notifiable diseases in the U.S.
National Health Surveys
health interviews of people
clinical tests, measurement, and physical examinations
survey of places where people receive medical care
NHIS NHANES BRFSS YBRS NHCS

16. Standardized Measurements of Health Status
Mortality Statistics
Life Expectancy
Years of Potential Life Lost
Disability-Adjusted Life years
Disability-Adjusted Life Expectancy

17. Epidemiological Study Measures
Probability statements or testing the differences in groups
Cohort Study
Relative Risk: measure of association between incidence of disease in unexposed group & exposed group
Case/Control Study
Odds Ratio: Estimates “relative risk” because incidence measures can not be obtained from two groups
Experimental
Use statistical t-test, or F-test to test probability of differences between groups

18. Epidemiological Studies
Descriptive Studies
“Who” or Person
Age, Sex, Ethnic, Race, Socioeconomic Status
“When” or Time
Time of day, week, month, season, year, decades
incubation period
“Where” or Place
country, state, county, street, urban or rural, domestic or foreign, institutional or noninstitutional.

19. Epidemiological Studies
Analytical Studies - testing of hypotheses about relationships between health problems
2 Basic Types
Case/Control Study (Retrospective)
Cohort Study (Prospective study)

20. Epidemiological Studies
Experimental
a study carried out under controlled conditions

21. Disease, Injury, and Death
Chapter 3
Epidemiology:
The Study of
Disease, Injury, and Death
in the Community