Week 1 - Overview of the Discipline of Epi & Descriptive Epidemiology Flashcards
What is the definition of Epidemiology?
A basic science that studies the determinants and distribution of a disease in a population in order to control a disease and illness and promote health
What are the STEPS Epidemiologists take? Data Source Assess Hypothesis Testing Action
Data Source = descriptive Epi. 3Ws Assessment = Inference (possibly stat analysis) Hypothesis Testing = Analytic Epi. (compare groups, rates, etc.) Action = community intervention
What are the STEPS Physicians take?
Date Source = history and physical exam Assessment = differential diagnosis Hypothesis testing = lab work, X-rays, etc. Action = diagnose/treatments
What are the objectives and activities in Epidemiology? (6)
- Identify patterns in groups over time. 2. Determine extent of the disease. 3. Identify causes of risk factors 4. Study the diseases natural course 5. Evaluate effectiveness of treatment and preventative measures 6. Develop public health policies in POPULATIONS
What are the Epidemiological assumptions? (3)
- Disease occurrence is not random 2. Systematic investigation of different populations can id associations and causal/preventative factors and changes/adjustments can improve health of that pop. 3. Making comparisons should be done for systematic disease assessments and investigations
What are the distribution factors? (2) (Description Epi 3Ws)
- Frequencies of occurrence - in relation to population size 2. Patterns of occurrence - person, place, time
What are the determinants? (4) (Analytic Epi 1W/1H)
Why/How 1. Factors of susceptibility/exposure/risk 2. Etiology/cause of disease 3. Mode(s) of transmission 4. Social/Environmental/Biological elements
What are the core functions of Epidemiology? (6)
- Public health surveillance (passive/active) 2. Field Investigation 3. Analytic studies 4. Evaluation 5. Linkages 6. Policy development
What is the purpose of public health surveillance? What are the key skills?
Find ongoing patterns, to develop, and apply investigation, control, and preventative measure. i.e. reportable disease registry (NNDSS/NEDSS), morbidity/mortality/birth registries Skills: data collection instruments, data management, data interpretation, scientific writing and presentation
What is the purpose of Analytic studies?
to advance the hypothesis that was generated. Key skills: design, conduct, analysis, interpretation and communication of research study data and findings
What is the purpose of Field investigation?
To determine the source of vehicle of disease, learn about its natural history, clinical spectrum; descriptive epi. i.e. ground beef as an E. coli source, eggs as Salmonella source
What is the purpose of Linkages?
To collaborate/link with other professionals
What is the purpose of policy development?
To provide input, testimony, and recommendations regarding disease control and prevention strategies, reportable disease regulations and health-care policy
What is descriptive epidemiology used for?
To know if a site/location is experiencing disease occurrence more frequently than usual. Must first determine the CASE definition (diagnostic criteria)
What are surveillance systems used for?
To determine if a disease is occurring and to count the frequency of that disease
What are the 2 surveillance systems?
Passive Active Syndromic - patients who have predefined systems/signs that are being reported or evaluated. Biosurveillance
What are CASE definitions?
Uniform criteria to define a disease/condition for public health surveillance to classify and count cases consistenly across reporting jurisdictions. Probable vs. Confirmed case definitions
Epidemic
Excess of normal expentancy; abnormally high
Outbreak/Cluster
Epidemic that’s limited to a localized increase, more concentrated area
Endemic
Constant presence within a given area/population in excess of normal levels elsewhere i.e. HIV in Africa
- There’s NO end!
Pandemic
Worldwide epidemic occurrence i.e. Swine Flu
What does the epidemic curve help us locate? (2)
What can they help us form hypothesis on? (3)
- Pattern of spread - (shape) common or point source (continous & intermittent)
- Magnitude of impact - sentinel case/peak/outliers, time trends (rate of occurrence), start/stop/duration
Hypothesis: routes of transmission, probably exposure period, incubation period
What is a common point source (common source outbreak)
An outbreak that comes from one source; common
What is the National Notifiable Diseases Surveillance System (NNDSS)?
A public health surveillance system that’s classified and counted by cases consistently; via a set of uniform criteria that’s used to define a disease/condition for this surveillance.
Syndromic Surveillance
A type of surveillance system where patients who have predefined signs/symptoms that are being reported or evaluated.
Sentinel/Index Case
peak/outliers/isolated case
How does a graph look that has an intermittent outbreak that is repeated?
Graphical representations of incubation periods on a graph:
What are the 3 basic types of relative measures of dieases frequencies utilized by epis?
- Ratios - division of 2 unrelated numbers (numerator is not apart of the denominator)
- Proportions - division of 2 related numbers (num is a subset of the denominator)
- Rates - division of 2 numbers with time in the denominator
Absolute differences
The absolute difference of two real numbers; the absolute value of their difference
Case Definitions
Clinical criteria on whether an individual is included as a case in an outbreak investigation
Case fatality rate
A measure of the severity of a disease, the proportion of reported cases of a specified condition/disease which are fatal within a specified time (measure of severity within a specified time)
Cumulative Incidence
The probability that a particular disease has occurred before a given time
Incidence
The occurrence, rate, or frequency of a disease
Incidence Rate
The number of new cases per population at risk in a given time period
Incidence density
- The number of new cases in a given area expressed at person-time of those AT RISK
When the denominator is the sum of the person-time of the at risk population
Period Prevalence
The proportion of a population that has the condition at some time during a given period, includes people who already have the condition at the start of the study period and during that period
Prevalence vs. Incidence
Prevalence is widespread; all affected individuals at a particular time.
Incidence is a measurement of the # of newly affected individuals who contract disease during a particular time period
Attack Rate/Incidence Proportion
The rate at which a new case occurs within a given time period; the demonimator is the population at risk
Crude Morbidity Rate
Disease rate with a given time span
Crude Mortality Rate
Death rate within a given time span
