Chapter 7 & 8 Epidemiology and Communicable Diseases Flashcards
WHO (World Health Organization) Epidemiology Definition
The study of the distribution and determinants of health-related states or events (including
disease), & the application of this study to the control of diseases and other health problems
What is the purpose of epidemiology?
Monitor the health of the population
Identify the determinants of health and disease in
communities
Investigate and evaluate interventions to prevent disease and maintain health
Endemic
Habitual presence of disease in particular geographic area
Epidemic
Occurrence of disease in excess of what is normally expected
Pandemic
Global epidemic
Epidemiologic Triad: Host
Age, sex, genetics
Epidemiologic Triad: Agent
Bacteria, virus, alcohol
Epidemiologic Triad: Environment
Humidity, access to nutritious food, crowding
Example of Epidemiologic Triad in Infectious Diseases
Infectious Disease: Chickenpox
Host: Age, immune system
Vector
Agent: Varicella zoster
Environment: Proximity to other kids (in school); season
Example of Epidemiologic Triad in Injuries
Ex) Injury related to Motor Vehicle Crash
- Host: Age
- Vector
- Agent: Energy transfer involved in impact
- Environment: Speed, texting, alcohol, time of day
Web of Casuality
Recognizes the complex interrelationships of many interacting factors
- Can be subtle
- Either increase or decrease the risk for disease or risk
Relationships are sometimes mutual w/ lines of causality going in both directions
Immunity
A host’s ability to resist a particular infectious disease-causing agent
Passive Immunity
Transfer of immunity from one person to another
Ex) Breastfeeding
Active Immunity
Immunizations
Antibodies develop in response to illness
Cross-immunity
Immunity to one agent provides immunity to a related
agent
Herd Immunity
The resistance of a group of people to an attack by disease to which a large proportion of the members of the group are immune
How does a population acquire herd immunity?
Natural infection & vaccination
When enough of the population is immune, even those who are not immunized are protected
Reproduction Number (R0)
Pronounced “R-naught”
The average number of people infected in a completely susceptible population
Reflects how efficiently the disease is transmitted
Ex) Measles R0 is between 12 and 18
R Effective (Rt)
Current reproduction number
Takes into account current susceptibility in the population
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
Things that are associated with increased likelihood of
the disease/health outcome
Population 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
Relative Risk (RR)
Measurement of relative risk ratio: incidence rate in exposed group/incidence rate in unexposed group
Risk of disease same with or without risk factor 1:1
considered relative risk of 1.0
- Relative risk > 1.0 indicates greater likelihood of acquiring disease
Interpretation:
Ex) Relative risk of 2.5 means that exposed group is 2.5 times more likely to acquire the disease than the unexposed group
How to Calculate RR Ratio
RR = Incidence in exposed group/ Incidence rate in
unexposed group
a (exposed & has disease)/a+b (exposed w/ no disease) divided by c(not exposed has disease)/c+d (not exposed w/ no disease)
