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Chapter 7
Epidemiology in Community Health
Care
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Historical Roots of Epidemiology
• Ancient Times: Hippocrates (460 to 375 BC)
• Middle Ages:1348 - Plague (“Black Death”)
• 18th century: Florence Nightingale (1820–1910)
• 19th century: Modern epidemiology (see Table 8-1)
– Causal thinking
– Sanitary statistics
– Infectious-disease epidemiology
– Chronic-disease epidemiology
• Current: Eco-epidemiology
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Host, Agent, and Environment Model
• Host
– Susceptible human or animal who harbors and
nourishes a disease-causing agent
• Agent
– A factor that causes or contributes to a health
problem or condition
• Environment
– All the external factors surrounding the host that
might influence vulnerability or resistance
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Theories of Causality in Health and Illness
• Relationship between a cause and its effect
– Chain of causation
– Causation in noninfectious disease:
environmental exposure and potential health
outcomes (9 elements)
– Multiple causation
• Dever’s epidemiological model, also called the
web of causation
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
Is the following statement true or false?
• The current thinking of epidemiology focuses on
causal thinking.
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
• False
– Current thinking of epidemiology is termed ecoepidemiology and is distinguished by
transforming global health patterns and
technological advances.
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Immunity
• A host’s ability to resist a particular infectious
disease-causing agent
– Passive immunity: short-term; acquired
naturally or artificially
– Active immunity: long-term, sometimes
lifelong; acquired naturally or artificially
– Cross-immunity: immunity to one agent
providing immunity to another related agent
– Herd immunity: immunity level present in a
population group
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Risk
• Probability that a disease or unfavorable health condition
will develop
• Directly influenced by biology, environment, lifestyle, and
system of health care.
• Risk factors: negative influences
• Epidemiologists studying populations at risk: collection of
people among whom a health problem has the possibility
of developing because certain influencing factors are
present or absent or because there are modifiable risk
factors
• Measurement of relative risk ratio: incidence rate in
exposed group/incidence rate in unexposed group
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Natural History of a Disease or Health
Condition
• Susceptibility stage
• Subclinical disease stage
– Incubation period
– Induction period
• Clinical disease stage
• Resolution stage
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Sources of Epidemiologic Information
• Vital statistics
• Census data
• Reportable diseases
• Disease registries
• Environmental monitoring
• National Center for Health Statistics health surveys
• Informal observational studies
• Scientific studies
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
During which stage would the community health nurse
first expect to see signs of a disease via laboratory
testing?
a. Susceptibility stage
b. Subclinical disease stage
c. Clinical disease stage
d. Resolution stage
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
c. Clinical disease stage
• During the clinical disease stage, signs and
symptoms develop, and in the early phase of this
period they may be evident only through laboratory
test findings. In the susceptibility stage, the disease
is not present and individuals have not been
exposed. During the subclinical disease stage,
individuals have been exposed but are
asymptomatic. During the resolution stage, the
disease causes sufficient changes to produce
recognizable signs and symptoms.
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Methods in Epidemiologic Investigative
Process
• Descriptive epidemiology
– Counts
– Rates
• Incidence: refers to all new cases of a disease
or health condition appearing during a given
time
• Number of persons developing a disease
Total number at risk per unit of time
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Methods in Epidemiologic Investigative
Process (cont.)
– Rates
• Prevalence: all of the people with a particular
health condition existing in a given population
at a given point in time
• Number of persons with a characteristic
Total number in population
– Computing rates
• Mortality
• Morbidity
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Methods in Epidemiologic Investigative
Process (cont.)
• Analytic epidemiology
– Prevalence studies
– Case-control studies
– Cohort studies
• Experimental epidemiology
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Research Process for an Epidemiologic
Study
1. Identify the problem.
2. Review the literature.
3. Design the study.
4. Collect the data.
5. Analyze the findings.
6. Develop conclusions and applications.
7. Disseminate the findings.
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
Is the following statement true or false?
• Analytic epidemiology involves cohort studies.
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
• True
– Analytic epidemiology attempts to identify
associations between a human disease or health
problem and its possible causes. Analytic studies
include prevalence studies, case-control studies,
and cohort studies.
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Internet Resources
• Association for Professionals in Infection Control and
Epidemiology, Inc.: http://www.apic.org
• Centers for Disease Control and Prevention:
http://www.cdc.gov
• Certification Board of Infection Control and
Epidemiology, Inc.: http://www.cbic.org
• Environmental Protection Agency:
http://www.epa.gov
• Immunization Action Coalition:
http://www.immunize.org
• National Center for Health Statistics:
http://www.cdc.gov/nchs/fastats/Default.htm
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins