Epidemiology: Key Concepts and Principles, Exams of Nursing

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Epidemiology is defined as? - ✅✅The STUDY of the DISTRIBUTION and DETERMINANTS of HEALTH-RELATED STATES OR EVENTS in specified POPULATIONS and the application of this knowledge to the CONTROL OF HEALTH PROBLEMS

What are the core Epidemiological Functions? - ✅✅Surveillance

Field Investigations

Analytic Studies

Evaluation

Linkages

Policy

What type of science is Epidemiology? - ✅✅Quantitative

What does measurement focus on in Epidemiology? - ✅✅Distribution and Determinants of health-related states and events

What can be said about the nature of epidemiology? - ✅✅Epidemiology is a story about health related states and events supported by data.

5 W's of Epidemiology? - ✅✅What

When

Where

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Who

Why

What are the two components of Epidemiology? - ✅✅Analytic and Descriptive

Descriptive Epidemiology Describes which elements? - ✅✅WHEN, WHERE, WHO

Time, Place, Person

Which elements does Descriptive Epidemiology study? - ✅✅The DISTRIBUTION, FREQUENCY, and PATTERN of health related states and events

Analytic Epidemiology describes which elements? - ✅✅WHY AND HOW

Analytic Epidemiology studies the? - ✅✅Determinants of health-related events. The WHY, the Causes

What are the four general categories to Determinants of Health? - ✅✅Biological, Environmental, Social, Health Behaviors

What makes up the social determinants of health? - ✅✅Economic Stability, Neighborhood/Built Environment, Health/Health Care, Social/Community Context, Education

What are examples of Health Behaviors? - ✅✅Nutrition, Physical Activity, Rest/Relaxation, Tobacco Use, Alcohol use, Illicit substance use, immunizations.

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Describe Multi-causality - ✅✅Etiology of all diseases is multifactoral.

What is the 'Causal Pie' Model made up of? - ✅✅Causative agent or event, characteristics of the person, characteristics of the environment, presence of preventative factors, action of catalysts or additive factors, mediating and moderating factors, interaction between the factors.

What does the Bradford Hill Criteria for Causation tell us? - ✅✅Several criteria are listed that help us determine if causal association is reasonable.

What does the Bradford Hill Criteria for causation not tell us? - ✅✅Statistical or clinical significance.

Occurrence of disease can be understood using which 3 models? -

✅✅Epidemiological Triad or Triangle, BEINGS Model, Web of causation.

What three aspects make up the Epidemiological Triad/Triangle? - ✅✅Agent, Host, Environment

acronmyn BEINGS Model of Disease Causation, what does it mean? - ✅✅Biological, Behavioral

Environmental

Immunological

Nutritional

Genetic

Services, Social, Spiritual

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What does the Web of Causation tell us? - ✅✅There are many different factors that make up chronic diseases and negative health conditions. Risk factors do not guarantee someone will get a disease.

What does Spectrum of Disease describe? - ✅✅The Severity of Disease

the severity of disease can vary from? - ✅✅Mild to fatal

What does the natural history of disease describe? - ✅✅The progression of the disease process over time in an untreated individual. Describes the STAGES of Disease

What are the different stages of disease? - ✅✅Susceptibility

Preclinical

Clinical

Recovery, Disability, Death

Preclinical is also known as? - ✅✅Subclinical, Presymptomatic or latent disease

What stage of disease does exposure take place? - ✅✅Stage of Preclinical/Subclinical/Presymptomatic/Latent Disease

When stage do the onset of symptoms take place? - ✅✅Stage of Clinical Disease

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When stage do pathologic changes occur? -

✅✅Preclinical/Subclinical/Presymptomatic/Latent Disease

What stage is the usual time of diagnosis? - ✅✅Stage of Clinical Disease

What stage may pathology be detected by screening? - ✅✅Subclinical Disease

What is true of infectious diseases in the stage of subclinical disease? - ✅✅This is their incubation period

What is true of chronic diseases in the stage of subclinical disease? - ✅✅This is their latency period.

What stage is the typical onset of Symptoms? - ✅✅Stage of Clinical Disease

What stage is primary prevention used in? - ✅✅The Stage of susceptibility

What is the focus of primary prevention? - ✅✅To protect against disease:

Place the host in good health

Immunizations

Public health measures

What stage of disease is Secondary Prevention used in? - ✅✅During the preclinical and early clinical stages of disease

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What does secondary prevention focus on? - ✅✅Early detection and prompt intervention to control the disease and minimize or eliminate complications.

Provide an example of Secondary prevention? - ✅✅COVID_19 Screening in asymptomatic patients

Are screening tests diagnostic? - ✅✅No they are not. They are used to identify people who might have a disease.

People who screen positive need what next? - ✅✅Need to have additional tests to confirm the presence of disease.

When is tertiary prevention used? - ✅✅During the advanced stage of clinical disease or when disability has occurred

What is the goal of tertiary prevention? - ✅✅To reduce the long term impact of disease and disability.

Primary Prevention occurs in which stage of disease? - ✅✅Stage of Susceptibility

Secondary Prevention occurs in which stage of disease? - ✅✅Preclinical/Subclinical/Presymptomatic/Latent disease

Which levels of prevention occur in the stage of clinical disease? - ✅✅Secondary prevention during the early part of stage

Tertiary prevention occurs during more advanced disease

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Define Communicability of Disease? - ✅✅The ability of a disease to be transmitted from one person to another OR to spread through the population.

What elements make up the Chain of infection? - ✅✅Reservoir

Portal of Exit

Transmission- Direct, Indirect, Airborne

Portal of Entry

Susceptible Host

Define Reservoir? - ✅✅Habitat in which the agent grows and lives

Reservoirs can be? - ✅✅Human

Animal

Invertebrates (insects, arachnoids)

Environment

Is the Reservoir always the source from which an agent is transferred to a host? -

✅✅No. For example the reservoir of Clostridium botulinum is soil but the source of most botulism infections is improperly canned food.

Do Reservoirs show the effects of illness? - ✅✅Not always

Define a carrier? - ✅✅A person with inapparent infection who is capable of transmitting the pathogen to others.

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Define Portal of Exit? - ✅✅The path by which a pathogen leaves it's host.

Examples of portal of exit? - ✅✅Respiratory Tract

Blood

Semen

Other body fluids

Crossing the placenta (mother-to-fetus)

blood sucking misquitos

What are the two main categories of mode of transmission? - ✅✅Direct and Indirect

Examples of two forms of direct transmission - ✅✅Direct contact, and Droplet Spread

Examples of three forms of indirect transmission - ✅✅Airborne, Vehicleborne, Vectorborne

Provide examples of direct transmission - ✅✅Direct Contact- Kissing, Sex, Soil contact

Provide examples of indirect transmission - ✅✅Vehicleborne

Vectorborne

Examples of vehicles - ✅✅Food, water, bedding, instruments

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Examples of Vectors - ✅✅Mosquitos, fleas, ticks

What is a fomite? - ✅✅Inanimate objects that may indirectly transmit an infectious agent. Such as tissues, bedding, or surgical scalpels.

Airborne transmission can be both direct and indirect. Why is this the case? -

✅✅Droplet= direct mode of transportation

Droplet nuclei= indirect mode of transportation

Describe different potential portal of Entry's - ✅✅Respiratory Tract, Mouth, Break in the skin or mucous membrane, surgical sites, catheters

What elements compromise a susceptible host? - ✅✅Immune Status, Overall Health, Nutritional Status

In terms of the chain of infection what does primary prevention include? -

✅✅Eliminate or sanitize the reservoir, Eliminate or cover the portal of exit, Eliminate or cleanse the transmission mode, cover or filter the portal of entry, Place the host in good health and immunize when available.

Describe the process of active immunity? - ✅✅Body produces its own antibodies in response to having been vaccinated or having a specific disease pathogen invade the body

Describe examples of passive immunity? - ✅✅Administration of immune globulin, Transplacental transfer of immune globulins to the fetus, transfer of antibodies and other immunoprotectant in human breast milk

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Define Herd Immunity? - ✅✅The resistance a population has to the invasion and spread of an infectious disease.

What is Herd Immunity based on? - ✅✅Based on the notion that if a population or group is mostly protected from a disease by immunizations then the chance of a major epidemic occurring is reduced.

What percentage of immunization in the population must be reached for herd

immunity to occur? - ✅✅At least 85%

What is cocooning? - ✅✅Used to protect infants from communicable diseases. Only family and friends who are fully immunized are allowed to be around the infant.

When is isolation used? - ✅✅Used in the inpatient setting (hospitals/nursing homes), used for persons who are known to be ill with a contagious disease.

State laws as well as accrediting organizations and isolation? - ✅✅Require one or two beds to be designated and as isolation beds.

When does Quarantine occur?? - ✅✅Used for persons who have been exposed to a contagious disease but may or may not become ill.

Example of Quarantine in action? - ✅✅Exposure to COVID19 quarantining at home.

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Descriptive epidemiology describes what? - ✅✅Frequency of events, and Pattern of Events (Who- Person, Where- Place, When- Time)

What graphics can be used to describe person? - ✅✅Tables, and Population Pyramid

What graphics can be used to describe place? - ✅✅Spot maps

What graphics can be used to describe time? - ✅✅Event Timelines

Define Public Health Surveillance - ✅✅Ongoing, systematic collection, analysis and interpretation of health-related data essential to information for the planning, implementation, and of public health practice, closely integrated with the timely dissemination of these data to those responsible for prevention and control

What does Public Health Surveillance use data for? - ✅✅To monitor health problems to facilitate their prevention or control.

What can information gained from surveillance be used for? - ✅✅Planning disease control and prevention programs, Policy-making

What are health indicators? - ✅✅Markers of health status. Anything that could effect health or illness is a health indicator.

List example health indicators - ✅✅physical or mental illness, impairments or disabilities, social well being, service provision, resource availability.

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What constitutes a notifiable disease in the United States? - ✅✅Diseases that are of considerable public health importance because of their seriousness- Cause serious morbidity or death, have the potential to spread, can be controlled with appropriate intervention.

What is true of Notifiable diseases in the US legally? - ✅✅Federal and State mandated reporting

List the measures of disease occurrence - ✅✅Counts- Number/Frequency, Ratios, Proportions, Percentages, Rates.

Ratios serve what function? - ✅✅Compare two things

How is a ratio calculated? - ✅✅By dividing the numerator by the denominator

What is true about the numerator in ratios? - ✅✅The numerator may or may not be part of the denominator. The numerator and denominator may or may not be related.

what is true about the numerator in Proportions? - ✅✅Numerator is always a part of the denominator

How are proportions usually calculated? - ✅✅As a decimal, example.

Characteristics of percentages? - ✅✅Numerator is always a part of the denominator. Just a proportion multiplied by 100.

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Define Rates? - ✅✅Frequency of an event in a population in a specified period of time.

What is always specified when determining rates? - ✅✅Population and Time period is always specified.

Three main categories of vital statistics? - ✅✅Mortality, Morbidity, Natality

Define mortality - ✅✅A mortality rate is a measure of the frequency of the occurrence of death in a defined population during a specific interval.

What do measures of natality include? - ✅✅Crude Birth rate, Crude fertility rate, low- birth weight ratio

What is the crude mortality rate? - ✅✅This is the mortality rate from ALL causes of death in a population. Per 100,

What is the infant mortality rate? - ✅✅Deaths of infants less than 1 year of age. Per 1,000 live births

What is the single most widely used health indicator to compare nations? - ✅✅Infant mortality rate

What is the neonatal mortality rate? - ✅✅Deaths of infants < 28 days of age, per 1,000 live births

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What is Perinatal mortality rate? - ✅✅deaths that occur from 28 weeks of gestation to 7 days after child is born

What is maternal mortality rate? - ✅✅Deaths of women due to pregnancy related causes during pregnancy or during the first 42 days after pregnancy termination regardless of the duration of the pregnancy, per 100,000 live births.

Define Morbidity - ✅✅Morbidity rate is a measure of the frequency of occurrence of disease or injury in a defined population during a specified interval.

What are the two major measures of disease frequency? - ✅✅Incidence and prevalence

What does prevalence refer to? - ✅✅The status of disease, not the onset

What does prevalence measure? - ✅✅The frequency of a disease at a particular point in time. Measures ALL cases (old and new) at a specified period of time.

How is prevalence calculated? - ✅✅As a proportion

Prevalence= - ✅✅Number of individuals who have a disease at a particular point in time/ Total population at risk at the specified time.

Point prevalence= - ✅✅Assessed at one specific point in time

Period prevalence= - ✅✅Assessed during a certain period.

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Incidence measures? - ✅✅The rate at which people without a disease develop the disease during a specified period.

Incidence is a measure of? - ✅✅The ONSET of disease. The APPEARANCE of disease. Measures the NEW

How is incidence proportion calculated? - ✅✅Number of NEW cases of a disease during a specified time period/ Population at risk of the disease at the start of that time period.

Incidence proportion is also known as? - ✅✅Risk, Attack Rate, Probability of developing a disease

How is Incidence Rate Calculated? - ✅✅Number of NEW cases of a disease in a specified time period/ Time that each person was observed, totaled for all persons.

What is Incidence rate also known as? - ✅✅Person-Time Rate

How does Incidence Rate differ from Incidence Proportion? - ✅✅More accurate estimate of risk, More difficult to calculate, Accounts for incomplete data. With a large population size calculating this could be very cumbersome.

What are the top three levels of Evidence - ✅✅Systematic Reviews (Meta Analysis), Randomized Controlled Trials, Nonrandomized Trials.

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What are the middle three levels of evidence? - ✅✅Cohort Studies, Case-control Studies, Cross-sectional studies.

What are the bottom two levels of evidence? - ✅✅Case reports/Case Series and Opinion/Experience/Theory

Describe characteristics of Systematic Reviews: Meta-Analyses - ✅✅Study of Studies, Method used in Cochrane Reviews and AHRQ Reviews, Very powerful methodology, Stringent Criteria for inclusion in the analysis, Quantitative analysis to combine and compare results of the studies.

Which studies are experimental? - ✅✅Randomized Trials and Non-Randomized trials (quasi-experiments)

Which studies always have an intervention? - ✅✅Randomized control trials and non randomized trials.

Which studies are considered observational studies? - ✅✅Cohort Studies, Case- control studies, Cross-sectional studies

Which studies are prospective? - ✅✅Randomized control trials, Quasi-experiments (non-randomized trials), Prospective Cohort Studies

Which Studies are retrospective in nature? - ✅✅Retrospective cohort studies, Case- control studies.

Are cross-sectional studies prospective or retrospective? - ✅✅They are neither.

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Characteristics to Randomized Control Trials - ✅✅Randomization to treatment group, Control of the intervention.

Characteristics to Non-randomized clinical trials (quasi-experiments) - ✅✅No randomization to treatment groups, comparison group may be different from the intervention group, control of the intervention.

Describe prospective cohort studies - ✅✅A group (cohort) of disease-free individuals is identified at one point in time and then followed over a period of time to determine whether the outcome (disease) occurs.

Describe Retrospective cohort studies - ✅✅Retrospective study that has a historical perspective. Requires access to information about the subjects before the exposure to disease causing factors and the onset of disease occurs. Often able to accomplish this when there are comprehensive medical records. Also known as historical cohort studies.

What is the type of study design in Case-Control - ✅✅Retrospective

How does a case-control study take place? - ✅✅Studies people who already have the disease and looks backward at exposure.

Describe the two groups in a Case-Control Study. - ✅✅Two groups of individuals are studied.

A group that has the disease under study (cases), A group that does not have the disease under study (controls)

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What is the primary purpose of Case-control studies - ✅✅Health information is examined to determine whether there are risk factors that may be related to their current disease.

What occurs in a cross-sectional study? - ✅✅A population is studied at a single point in time. Participants are asked about their current disease state and their exposures to certain factors.

What are cross-sectional survey's also known as? - ✅✅Prevalence Studies. Considered to be the weakest study design.

Define Risk - ✅✅The probability that an event will occur

How is risk calculated? - ✅✅As a proportion

Risk is the same as what? - ✅✅Incidence proportion

How is risk presented? And what can it vary from? - ✅✅As a probability, and can vary from 0-1.0.

What are the two types of risk? - ✅✅Absolute Risk and Attributable Risk

What is absolute risk? - ✅✅The overall incidence of the disease in a specified population.

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How is absolute risk calculated? - ✅✅Calculated the same as incidence proportion.

Define Attributable Risk - ✅✅The amount of disease associated with a causative factor in a specified population.

What are measures of association used for? - ✅✅To compare the occurrence of disease in one group with the occurrence of disease in another group.

What are two measures used for association? - ✅✅Risk Ratio/Relative Risk (RR) and Odds Ratio (OR).

Define Relative risk - ✅✅Relative risk is a measure of association between the exposure to a particular factor and the risk of a particular disease or outcome.

What type of studies can calculate relative risk - ✅✅Prospective Studies

When is the odds ratio used over the risk ratio/relative risk? - ✅✅When the RR cannot be calculated. Used in case-control and other RETROspective studies.

RR or OR= 1? - ✅✅Risk/Odds in the exposed is equal to the risk/odds in the non- exposed group

RR or OR >1 - ✅✅Risk/Odds in the exposed group is greater than the risk/odds in the non-exposed group.

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RR or OR <1 - ✅✅Risk or Odds in the exposed group is less than the risk/odds in the non-exposed group.

Why do confidence intervals need to be calculated for Risk ratios and odds ratios. -

✅✅Because RR and OR are estimates. They need a confidence interval associated with them.

If the confidence interval includes 1 what does this mean? - ✅✅There is not a difference between the exposed or unexposed groups.

If the confidence interval does not include 1 what does this mean? - ✅✅There is a difference between groups

If there is a difference between groups with the confidence interval, what do you then

determine? - ✅✅You have to determine whether the difference is increased or decreased. This is done through interpretation of the RR o OR.

What is the purpose of health screening? - ✅✅To promote detection of diseases in their earliest stages, when treatment has the greatest chance of working, in order to reduce morbidity and mortality.

What type of prevention does health screening fall under? - ✅✅Secondary.

What occurs in the subclincal disease stage? - ✅✅Symptoms are not apparent or asymptomatic, Pathological changes occur and some can be detected by screening. This is the incubation period for infectious diseases and the Latency period for chronic diseases.

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Define Sensitivity - ✅✅Probability that a person with the disease will test positive for the disease (true positive). The ability of tests to correctly identify those with the disease. Probability of correctly identifying the disease.

Define Specificity - ✅✅Probability that a person who does not have the disease will test negative for the disease (true negative). The ability of the test to correctly identify those without the disease.

Define Positive Predictive Value - ✅✅Probability that a person who has a positive test actually has the disease. Proportion of people with a positive test result who have the disease.

What influences the Positive Predictive Value? - ✅✅Prevalence influences the PPV. When you are looking for a disease that is very rare a positive screening test result is more likely to be a false positive than a positive test result in a population where a large percentage of the population has the disease.

Define negative predictive value - ✅✅Probability that a person who has a negative test does not have the disease. Proportion of people with a negative test result who do not have the disease.

What is the effect of prevalence on negative predictive value. - ✅✅As prevalence increases negative predictive value decreases.

Case= - ✅✅An individual who has the disease, disorder, injury, health behavior, or health event of interest

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Primary case= - ✅✅First case of the disease or condition or behavior

Index case= - ✅✅First case brought to the epidemiologists attention (not necessarily the primary case)

Secondary cases= - ✅✅Cases that became ill after the disease was introduced into the population and become infected from the primary case.

Suspect case= - ✅✅An individual who has all of the signs and symptoms of a disease or condition, yet not diagnosed.

Confirmed= - ✅✅All criteria are met.

Endemic= - ✅✅Amount of disease usually present in a community

Hyperendemic= - ✅✅Persistent high levels of disease

Sporadic= - ✅✅Occurs infrequently and irregularly

Epidemic= - ✅✅An increase in the number of cases above what is expected in the population in that area.

Outbreak= - ✅✅An epidemic but in a limited geographical area

Pandemic= - ✅✅Epidemic that has spread over several countries or continents.

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Types of Spread in Epidemic - ✅✅Common Source, Propagated, Mixed

Define Common Source - ✅✅attributed to a specific source

Define Propagated Source - ✅✅Transmitted from person to person

Define Mixed Epidemic - ✅✅Stats with a common source and then spread by person- to-person contact.

Which statistic is especially good at investigating disease outbreaks - ✅✅Attack Rates- They describe rapidly occurring new cases of disease in a well identified population over a limited time period.

What type of study is especially suited for studying outbreaks? - ✅✅Case Control

During a field investigation what takes place in establishing criteria for case

identification. - ✅✅Standard Clinical Criteria (What), Loose case definition vs. strict case definition. A case may be further characterized by Who, Where, and When.

How are cases counted during field investigations - ✅✅Using standard descriptive statistics. exposure status and disease frequency need to be determined and compared with the appropriate at-risk population.

How is time examined? - ✅✅Epidemic Curve

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How are epidemic curves classified? - ✅✅Epidemic Curve- Common source vs. propagated vs. mixed

What can only be calculated through prospective studies? - ✅✅Relative Risk

Which study is always retrospective? - ✅✅Case-Control

An Epidemic Curve can be used to describe what characteristic of health-related

states/events - ✅✅Time

What is the function of Adjusted Rates? - ✅✅Adjusted Rates are used to control for the effects of variables such as age on a health outcome

What elements must be present in a rate? - ✅✅Period of time, It is always a Ratio, Population

Which Study designs are descriptive in nature? - ✅✅Cross sectional study and Ecological Study