Descriptive Epidemiology & Measures of Disease Frequency Flashcards
Name the surveillance systems
- Passive
- Active
- Syndromic
Describe Passive Surveillance
Relies on HS to follow regulations on required reportable diseases/conditions
PHS tracks disease frequency/occurrence over time and within populations
Describe Active Surveillance
Public health officials go into communities to search for new ideas/condition cases
Describe Syndromic Surveillance
A system that looks for pre-defined signs/symptoms of patients related to trackable-but-rare disease/conditions
What is Biosurveillance and what system is it apart of?
Surveillance of human, animal, plant, and environment
Apart of the syndromic surveillance
What are the four stages of natural history of disease timeline?
- Stage of Susceptibility
- Stage of Subclinical Disease
- Stage of Clinical Diseases
- Stage of Recovery, Disability, or Death
What occurs between the Stage of Susceptibility and the Stage of Subclinical Disease?
Exposure
What occurs during the Stage of Susceptibility?
Pathologic changes
What occurs between the Stage of Subclinical Disease and the Stage of Clinical Disease?
Onset of symptoms
What occurs early in the Stage of Clinical Disease?
Usual time of diagnosis
What is Induction/Incubation?
Time between exposure and onset of disease
What is the latency period?
Time between onset of disease and disease detection (symptoms or diagnosis)
What is a Case Definition?
A set of uniform criteria used to define a disease/condition for public health surveillance
Enables public health to classify and count cases consistently across reporting jurisdictions
What is the CSTE?
Council of State and Territorial Epidemiologists
What is the importance of the CSTE’s position statements?
These are used each year to provide uniform criteria of nationally notifiable infection and non-infectious conditions for reporting purposes
Define Epidemic
Occurrence of disease clearly in excess of normal expectancy
Community/Period clearly defined
Define Outbreak
An epidemic limited to a localized increase in the occurrence of disease
Sometimes interchanged with “Cluster”
Define Endemic
The constant presence of a disease within a given area or population in excess of normal levels in other areas
Define Emergency of International Concern
An epidemic that alerts the world to the need for high vigilance (pre-pandemic labeling)
Define Pandemic
An epidemic spread world-wide (global health impact)
Multi-national/multi-continent
What is the Epidemic Curve?
A graphical, time-based depiction generated during an outbreak/epidemic reflecting the # of cases; by date
A histogram incorporating all 3 elements of descriptive epidemiology
What are the two things the Epi Curve can visually depict?
- Magnitude and Timing of disease occurrence
2. Pattern (shape) of disease occurrence
What is seen with the Magnitude and Timing of disease occurrence on the Epi Curve?
- Sentinel or index case/peak/outliers
- Start/stop/duration
What is seen with the Pattern of the Epi Curve?
- Common/Point Source (Continuous, Intermittent)
- Propogated
What is a common/point source?
Derived from a common, single point source for the outbreak
What is a propagated source?
Person-to-person
What are the three types of relative measures of disease frequencies?
- Proportions
- Ratios
- Rates
What is a proportion?
Division of 2 related numbers; numerator is subset of denominator
What is a ratio?
Division of 2 unrelated numbers; numerator is not a subset fo the denominator
What is a rate?
A proportion with time incorporated into the denominator
What are the three key factors in comparing measures of disease frequency between groups?
- # of ppl 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
How does epi work to compare the burden?
Standardization
Define Incidence
New cases of disease
Define Prevalence
Existing cases of disease + new cases of disease
How do you leave the bathtub?
Cured, death
How do you stay in the bathtub longer?
Treatment
How do you calculate incidence?
(# new cases of illness / # ppl at risk of illness or in pop)
What is one crucial factor to remember in calculating incidence?
Subtract from starting population those who already have the disease or are immune to the disease (those who are not at risk)
How else can incidence be referred to?
Risk or attack rate
What sort of population is incidence useful for?
Non-dynamic; time frames for numerator and denominator are the same
What is Cumulative Incidence?
Incidence summed over multiple time periods
What is Person-Time?
Product of # of ppl and length of time they are followed for
How do you calculated Incidence Rate?
(# new cases disease / person-time at risk for the disease or in the pop)
What sort of population is incidence rate useful for?
Dynamic populations; the denominator is commonly estimated (pop at certain time, avg pop throughout the yr)
What is Incidence Density?
Incidence Rate summed over multiple time periods
How do you calculate Prevalence?
(# existing cases of a disease / # persons in population)
What is Point Prevalence?
Prevalence at a given point in time
What is Period Prevalence?
Prevalence over a given period of time
How do you calculate Crude Morbidity Rate?
(# persons w/ disease / # persons in population)
How do you calculate Crude Mortality Rate?
(# deaths – all causes / # persons in population)
How do you calculate Cause-Specific Morbidity Rate?
(# persons w/ cause-speficic disease / # persons in population)
How do you calculate Cause-Specific Mortality Rate?
(# cause-specific deaths / # of persons in population)
How do you calculate Case-Fatality Rate?
(# cause-specific deaths / # cases of disease)
How do you calculate Cause-Specific Survival Rate?
(# cause-specific cases alive / # cases of disease) something about all individuals of pop
How do you calculate Proportional Mortality Rate (PMR)?
(# cause-specific deaths / total # deaths in population)
How do you calculate Live-Birth Rate?
(# live births / 1,000 population)
How do you calculate Fertility Rate?
(# live births / 1,000 women childbearing age)
How do you calculate Neonatal Mortality Rate?
(# deaths in those <28 days of age / 1,000 live births)
How do you calculate Postnatal Mortality Rate?
(# deaths in those >/= 28 days but <1 yr of age / 1,000 live births)
How do you calculate Infant Mortality Rate?
(# deaths in those <1 yr of age / 1,000 live births)
How do you calculate Maternal Mortality Ratio?
(# female deaths related to pregnancy / 100,000 live births)
What is infectivity?
Ability to invade a pt
infected / # susceptible
What is pathogenicity?
Ability to cause a clinical disease
w/ clinical disease / # infected
What is virulence?
Ability to cause death
deaths / # w/ infectious disease
