Segars: Epidemiology Flashcards
What is epidemiology?
- a public health-discipline basic science which studies the…
- distribution
- determinants
- … of disease in populations to control disease and illness, and promote health
What are the 3 W’s of patterns of disease ocurrences?
- Who
- Where
- When
- this is descriptive epidemiology
What can descriptive epidemiology be used for?
-to know if a location is experiencing disease occurrence more frequently than usual or more than other locations
What are the 3 key factors in comparing measures of disease frequency between groups
- # of people affected/impacted (frequency/count)
- Size of the source population (from which disease cases or outcomes arose) or those at risk
- Length of time the “population” is followed
Passive surveillance system?
-relies on healthcare system to follow regulations on required reportable diseases/conditions
Active surveillance system
-public health officials go into communities to search for new disease/condition cases
Syndromic surveillance system
-a system that looks for pre-defined signs/symptoms of pts related to trackable-but-rare diseases/conditions
What is an epidemic
-occurrence of disease clearly in excess of normal expectancy
What is an outbreak
- an epidemic limited to a localized increase in the occurrence of disease
- sometimes interchanged with “cluster”
Endemic
-the contant presence of a disease within a given area or population in excess of normal levels in other areas
Emergency of international concern
-an epidemic that alerts the world to the need for high vigilance (pre pandemic)
Pandemic
- an epidemic spread world-wide (global health)
- multi national/ multi continent
What are some epidemiological assumptions?
- disease occurrence is not random
- systematic investigation of different populations can identify associations and causal/preventive factors and impact of changes can impart on health of population
- making comparisons is the cornerstone of systematic disease assessments/investigations
What are the determinants of disease?
- factors of susceptibility/exposure/risk
- etiology/causes of disease
- Modes of transmission
- social/environmental/biologic elements that determine the occurrence/presence of disease
What are the 3 types of frequencies utilized to measure disease frequencies?
- proportions: division of 2 related numbers (the numerator is a subset of the denominator)
- Ratios: division of 2 unrelated numbers (numerator is not a subset of the denominator)
- Rates: division of 2 numbers with time included in the denominator
What is incidence
-NEW occurrences of an outcome/disease
What is prevalence
- EXISTING occurrences of an outcome/disease
- includes old and new cases, collectively
What are both incidence and prevalence?
- a proportion!
- a simple percentage
- part over whole
What is the formula for incidence?
- # of new cases of illness/# of people at risk of illness
- ALWAYS subtract out (from the starting population), those who not at risk (already have the disease or are immune)
What is the formula for prevalence?
- total # of cases of illness/# of people in population
- remember that there is point prevalence and period prevalence
What is infectivity
- the ability to invade a patient (host)
- #infected/# susceptible (at risk)
Pathogenicity?
- the ability to cause clinical disease
- # with clinical disease/ #infected
What is virulence
- the ability to cause death
- # of deaths/# with infectious disease
- synonymous with case-fatality rate
What is crude morbidity rate?
-# of persons with disease/ # of persons in population
