1. What is Epidemiology? (1)
Epidemiologic basis of public health
What is Epidemiology? (1)
Epidemiology is that field of medical science which is concerned with the relationship of various factors and conditions which determine the frequencies and distributions of an infectious process, a disease, or a physiologic state in a human community. (Maxcy)
Detels - PH Oct 2013

2. What is Epidemiology? (2)
Epidemiologic basis of public health
What is Epidemiology? (2)
Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to control of health problems (Last)
Detels - PH Oct 2013

3. What is Epidemiology? (3)
Epidemiologic basis of public health
What is Epidemiology? (3)
Epidemiology is a strategy for the study of factors relating to the etiology, prevention, and control of disease; to promote health; and to efficiently allocate efforts and resources for health promotion, maintenance and medical care in human populations.
(Detels)
Detels - PH Oct 2013

4. Epidemiologic basis of public health
EPI DEMOS LOGOS
upon people study
Epidemiology is a philosophy, a strategy, a methodology, a way of studying a health problem. Epidemiology is not a body of knowledge.
Detels - PH Oct 2013

5. Two Holy Trinities of Epidemiology
Epidemiologic basis of public health
Two Holy Trinities of Epidemiology
Disease characteristics: agent
host
environment
Health is a state of equilibrium between:
Agent Host 
Environment
Detels - PH Oct 2013

6. Two Holy Trinities of Epidemiology (2)
Epidemiologic basis of public health
Two Holy Trinities of Epidemiology (2)
Disease descriptors: Time
Place
Person
Epidemiologists describe disease/states in terms of time, place and person
Detels - PH Oct 2013

7. Ultimate truth = denominator
Epidemiologic basis of public health
Ultimate truth = denominator
Detels - PH Oct 2013

8. Epidemiologic basis of public health
Incidence =
# of New Cases Occurring in a Given
Population in a Specified Time Period_
Population at Risk in That Time Period (Speedometer)
Detels - PH Oct 2013

9. Epidemiologic basis of public health
Prevalence =
# of Cases Existing in a Given
Population at a Single Point in Time__
Population at That Time
(odometer)
Detels - PH Oct 2013

10. Epidemiologic basis of public health
An example of the use of time, place, and person to describe disease characteristics:
Gathering evidence
Ordering hypotheses by probability
Observing place, time (trend), and
person characteristics
Detels - PH Oct 2013

11. Epidemiologic basis of public health
Detels - PH Oct 2013

12. Epidemiologic basis of public health
Detels - PH Oct 2013

13. Epidemiologic basis of public health
Detels - PH Oct 2013

14. Epidemiologic basis of public health
Detels - PH Oct 2013

15. Epidemiologic basis of public health
Detels - PH Oct 2013

16. Epidemiologic basis of public health
Detels - PH Oct 2013

17. Epidemiologic basis of public health
Detels - PH Oct 2013

18. Epidemiologic basis of public health
Detels - PH Oct 2013

19. Epidemiologic basis of public health
Detels - PH Oct 2013

20. Epidemiologic basis of public health
Reported incidence of disease X , Los Angeles
Detels - PH Oct 2013

21. WHAT DRIVES AN EPIDEMIC
Reproductive number – number of secondary infections from one case
Transmission probability per contact
Contact rate/frequency
Duration of infectiousness
Available susceptibles
Agent characteristics

22. REPRODUCTIVE NUMBER
R = number of secondary infections from one individual
Ro = reproductive at the beginning of epidemic
R > 1 Epidemic spreads
R < 1 Epidemic dies out
R subject to changes in presence and levels of determinants of epidemic spread

23. Epidemiologic basis of public health
Public health is concerned with health of the public; i.e., populations. Epidemiology is the method/strategy of studying disease/health in human populations. Epidemiology is therefore the core science of public health.
Detels - PH Oct 2013

24. Uses of Epidemiology (1)
Epidemiologic basis of public health
Uses of Epidemiology (1)
a. Community diagnosis; i.e., what are the major health problems occurring in a community
b. Establishing the history of a disease in a population; e.g., identifying the periodicity of an infectious disease
c. Describing the natural history of disease in the individual; e.g., natural history of HIV infection in the individual (infection-acute syndrome-asymptomatic phase-clinical disease-death)
Detels - PH Oct 2013

25. Uses of Epidemiology (2)
Epidemiologic basis of public health
Uses of Epidemiology (2)
d. Describing the clinical picture of disease; i.e., who gets the disease, who dies from the disease, and what the outcome of the disease is
Estimating risk; e.g., what factors increase the risk of heart disease, automobile accidents, and violence
f. Identifying syndromes and precursors; e.g., the relationship of high blood pressure to stroke, kidney disease, and heart disease
Detels - PH Oct 2013

26. Uses of Epidemiology (3)
Epidemiologic basis of public health
Uses of Epidemiology (3)
g. Evaluating prevention/intervention programs; e.g., vaccine and clinical trials
h. Investigating epidemics/diseases of unknown etiology
i. Assessing the cost-effectiveness of interventions
j. Assessing strategies to translate science to action (“implementation science”)
Detels - PH Oct 2013