What is the definition of epidemiology?
Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to control health problems.
Source: CDC Principles of Epidemiology
What is the natural history of a disease?
The natural history of a disease refers to the progression of a disease process in an individual over time, from the onset to resolution or chronicity.
Source: Merck Veterinary Manual
What are the three components of the epidemiologic triad?
The three components of the epidemiologic triad are the agent, the host, and the environment.
Source: CDC Principles of Epidemiology
What is an epidemic?
An epidemic is the occurrence of more cases of a disease than expected in a given area or among a specific group of people over a particular period of time.
Source: Principles of Epidemiology
What is the difference between incidence and prevalence?
Incidence refers to the number of new cases of a disease in a population during a specific time, while prevalence refers to the total number of cases, both new and existing, in a population at a specific time.
Source: Merck Veterinary Manual
What is a case-control study?
A case-control study is a type of observational study that compares individuals with a specific condition (cases) to those without the condition (controls) to identify risk factors.
Source: Principles of Epidemiology
What is herd immunity?
Herd immunity occurs when a large portion of a population becomes immune to a disease, making its spread unlikely.
Source: CDC Principles of Epidemiology
What is the primary purpose of descriptive epidemiology?
The primary purpose of descriptive epidemiology is to describe the distribution of diseases and health outcomes in terms of person, place, and time.
Source: Principles of Epidemiology
What is the role of an epidemiologist?
An epidemiologist studies the distribution and determinants of health-related states or events and applies this knowledge to control health problems.
Source: Principles of Epidemiology
What is a cohort study?
A cohort study is a type of observational study where a group of individuals who share a common characteristic is followed over time to observe outcomes.
Source: Merck Veterinary Manual
What is a pandemic?
A pandemic is an epidemic that has spread over several countries or continents, usually affecting a large number of people.
Source: Principles of Epidemiology
What is the difference between a retrospective and a prospective study?
A retrospective study looks backward in time to examine exposure to risk factors, while a prospective study follows participants forward in time to observe outcomes.
Source: Gordis Epidemiology
What is a cross-sectional study?
A cross-sectional study examines data on exposure and outcome at the same point in time in a population.
Source: Merck Veterinary Manual
What are the steps of an outbreak investigation?
Key steps include: establish a case definition, confirm the outbreak, identify cases, describe and orient data in terms of time, place, and person, develop hypotheses, test hypotheses, refine hypotheses, and implement control measures.
Source: CDC Principles of Epidemiology
What is an endemic?
An endemic is the constant presence of a disease or infectious agent within a given geographic area or population group.
Source: Principles of Epidemiology
What is the purpose of analytical epidemiology?
Analytical epidemiology seeks to identify causes or risk factors for diseases and health-related events by testing specific hypotheses.
Source: Gordis Epidemiology
What is attributable risk?
Attributable risk is the difference in disease risk between exposed and unexposed groups, showing the amount of disease risk that can be attributed to a specific exposure.
Source: Merck Veterinary Manual
What is the incubation period?
The incubation period is the time interval between exposure to an infectious agent and the appearance of the first signs or symptoms of the disease.
Source: Principles of Epidemiology
What is the purpose of a case definition?
A case definition provides a set of standard criteria for classifying whether an individual has a particular disease or health condition.
Source: CDC Principles of Epidemiology
What is a confounding variable?
A confounding variable is an extraneous factor that can distort the observed relationship between an exposure and an outcome.
Source: Gordis Epidemiology
What is a point source epidemic?
A point source epidemic occurs when a group of people is exposed to the same source of infection at the same time.
Source: Principles of Epidemiology
What is a propagating epidemic?
A propagating epidemic occurs when the infection spreads person-to-person over time.
Source: CDC Principles of Epidemiology
What is a secondary attack rate?
The secondary attack rate is the proportion of susceptible individuals who develop the disease after exposure to a primary case.
Source: Gordis Epidemiology
What is the iceberg concept of disease?
The iceberg concept refers to the idea that for every clinically apparent case of disease, there are many subclinical, undiagnosed, or asymptomatic cases.
Source: Principles of Epidemiology
What is surveillance in epidemiology?
Surveillance is the ongoing systematic collection, analysis, and interpretation of health data for planning, implementation, and evaluation of public health practice.
Source: CDC Principles of Epidemiology
What is the difference between active and passive surveillance?
Active surveillance involves proactive data collection by health authorities, while passive surveillance relies on reports submitted by health providers.
Source: Gordis Epidemiology
What is the basic reproductive number (R0)?
The basic reproductive number (R0) is the average number of secondary cases produced by one primary case in a completely susceptible population.
Source: Principles of Epidemiology
What is an odds ratio?
An odds ratio is a measure of association that quantifies the odds of exposure among cases relative to the odds of exposure among controls.
Source: Gordis Epidemiology
What is a confidence interval?
A confidence interval is a range of values that likely contain the true value of a parameter, calculated from sample data.
Source: Merck Veterinary Manual
What is the null hypothesis in epidemiology?
The null hypothesis is the assumption that there is no association between exposure and outcome.
Source: Principles of Epidemiology
What is the role of randomization in a clinical trial?
Randomization helps ensure that treatment groups are comparable and eliminates bias in the allocation of treatments.
Source: Gordis Epidemiology
What is a p-value in epidemiology?
A p-value indicates the probability of observing the study results, or something more extreme, if the null hypothesis is true.
Source: Principles of Epidemiology
What is a Type I error?
A Type I error occurs when a null hypothesis is rejected even though it is true.
Source: Merck Veterinary Manual
What is a Type II error?
A Type II error occurs when a null hypothesis is not rejected even though it is false.
Source: Gordis Epidemiology
What is recall bias?
Recall bias occurs when there are differences in the accuracy or completeness of the information recalled by study participants.
Source: Principles of Epidemiology
What is selection bias?
Selection bias occurs when the sample selected for a study is not representative of the target population.
Source: Merck Veterinary Manual
What is effect modification?
Effect modification occurs when the effect of an exposure on an outcome differs depending on the level of another variable.
Source: Gordis Epidemiology
What is the purpose of matching in a case-control study?
Matching is used to control confounding by ensuring cases and controls are comparable for specific variables.
Source: Principles of Epidemiology
What is lead-time bias?
Lead-time bias occurs when earlier detection of a disease falsely appears to improve survival rates without actual improvements in outcomes.
Source: Merck Veterinary Manual
What is length-time bias?
Length-time bias occurs when slower-progressing, less aggressive cases of a disease are more likely to be detected by screening than fast-progressing cases.
Source: Gordis Epidemiology
What is primary prevention?
Primary prevention involves measures taken to prevent the occurrence of disease, such as vaccination or lifestyle modifications.
Source: Principles of Epidemiology
What is secondary prevention?
Secondary prevention focuses on early detection and intervention to stop the progression of a disease.
Source: Gordis Epidemiology
What is tertiary prevention?
Tertiary prevention involves measures to reduce complications and improve quality of life for people with a disease.
Source: Merck Veterinary Manual
What is the difference between sensitivity and specificity?
Sensitivity is the ability of a test to correctly identify those with the disease, while specificity is the ability to correctly identify those without the disease.
Source: CDC Principles of Epidemiology
What is the purpose of a control group in a study?
The control group provides a baseline for comparison to determine the effect of an exposure or intervention.
Source: Principles of Epidemiology
What is a risk ratio?
A risk ratio compares the risk of a health outcome in an exposed group to the risk in an unexposed group.
Source: Gordis Epidemiology
What is a case-fatality rate?
The case-fatality rate is the proportion of individuals with a specific condition who die from that condition within a specified time.
Source: Merck Veterinary Manual
What is a p-value?
A p-value is the probability of obtaining the observed results, or more extreme ones, assuming the null hypothesis is true.
Source: Gordis Epidemiology
What is confounding in epidemiology?
Confounding occurs when an extraneous variable is associated with both the exposure and the outcome, distorting the true relationship.
Source: Principles of Epidemiology
What is an attributable fraction?
The attributable fraction is the proportion of cases in the population that can be attributed to a specific exposure.
Source: Merck Veterinary Manual
What is a standard error?
The standard error is the standard deviation of the sampling distribution of a statistic, measuring its precision.
Source: CDC Principles of Epidemiology
What is the difference between absolute risk reduction and relative risk reduction?
Absolute risk reduction is the difference in risk between two groups, while relative risk reduction is the proportionate reduction in risk.
Source: Gordis Epidemiology
What is an ecological study?
An ecological study analyzes data at the population or group level rather than the individual level.
Source: Principles of Epidemiology
What is statistical power?
Statistical power is the probability of correctly rejecting the null hypothesis when it is false.
Source: Merck Veterinary Manual
What is the Kaplan-Meier method?
The Kaplan-Meier method is a statistical technique used to estimate survival probabilities over time.
Source: CDC Principles of Epidemiology
What is a hazard ratio?
A hazard ratio is a measure of how often a particular event happens in one group compared to another over time.
Source: Gordis Epidemiology
What is the difference between correlation and causation?
Correlation is a statistical association between two variables, while causation indicates one variable directly affects the other.
Source: Principles of Epidemiology
What is a cohort study?
A cohort study follows a group of individuals over time to determine the incidence of disease and its association with exposures.
Source: Principles of Epidemiology
What is a case definition in an outbreak investigation?
A case definition is a set of standard criteria used to classify whether an individual has a specific disease or condition.
Source: CDC Principles of Epidemiology
What is the difference between a pandemic and an epidemic?
An epidemic is localized to a specific region or population, while a pandemic spans multiple countries or continents.
Source: Gordis Epidemiology
What is the role of surveillance in public health?
Surveillance monitors disease trends and provides data for planning, implementing, and evaluating public health interventions.
Source: Principles of Epidemiology
What is the attack rate in epidemiology?
The attack rate is the proportion of people who develop a disease among those at risk during a specific time.
Source: Merck Veterinary Manual
What is the difference between cross-sectional and longitudinal studies?
Cross-sectional studies assess data at one point in time, while longitudinal studies collect data over a period of time.
Source: Gordis Epidemiology
What is a confounding variable?
A confounding variable is an external factor that distorts the observed relationship between exposure and outcome.
Source: Principles of Epidemiology
What is a null hypothesis?
The null hypothesis assumes no association between exposure and outcome, serving as a baseline for testing.
Source: CDC Principles of Epidemiology
What is lead-time bias?
Lead-time bias occurs when earlier detection of a disease falsely appears to improve survival rates without affecting outcomes.
Source: Gordis Epidemiology
What is ecological fallacy?
Ecological fallacy occurs when assumptions about individuals are based on group-level data.
Source: Principles of Epidemiology
What is an odds ratio?
An odds ratio quantifies the odds of exposure among cases relative to controls, used in case-control studies.
Source: Merck Veterinary Manual
What is statistical significance?
Statistical significance indicates the likelihood that observed results are not due to chance, typically assessed with a p-value.
Source: Gordis Epidemiology
What is herd immunity?
Herd immunity occurs when enough people in a population are immune to a disease, reducing its spread.
Source: Principles of Epidemiology
What is the purpose of randomization in clinical trials?
Randomization eliminates selection bias by assigning participants to treatment groups by chance.
Source: CDC Principles of Epidemiology
What is bias in epidemiological studies?
Bias is a systematic error in study design or data analysis that leads to incorrect conclusions.
Source: Gordis Epidemiology
What is length-time bias?
Length-time bias occurs when slower-progressing diseases are more likely to be detected by screening, giving a false impression of improved survival.
Source: Principles of Epidemiology
What is a p-value?
A p-value is the probability of obtaining results as extreme as those observed, assuming the null hypothesis is true.
Source: Gordis Epidemiology
What is a Kaplan-Meier curve?
A Kaplan-Meier curve is a graphical representation of survival probabilities over time.
Source: CDC Principles of Epidemiology
What is the purpose of blinding in a study?
Blinding prevents bias by ensuring that participants and/or researchers do not know who is receiving the treatment or placebo.
Source: Gordis Epidemiology
What is an attributable risk percent?
An attributable risk percent quantifies the proportion of the risk of a disease in the exposed group that is due to the exposure.
Source: Principles of Epidemiology
What is an epidemic curve?
An epidemic curve is a graphical representation of the number of cases of disease over time.
Source: Merck Veterinary Manual
What is a secondary attack rate?
The secondary attack rate measures the spread of disease in a specific group, typically among contacts of primary cases.
Source: Gordis Epidemiology
What is a confidence interval?
A confidence interval is a range of values that is likely to contain the true population parameter.
Source: Principles of Epidemiology
What is incidence density?
Incidence density is the rate of new cases of a disease per unit of person-time at risk.
Source: Merck Veterinary Manual
What is a proportional mortality ratio?
A proportional mortality ratio compares the number of deaths from a specific cause to the total number of deaths in a population.
Source: CDC Principles of Epidemiology
What is relative risk reduction?
Relative risk reduction is the proportional decrease in risk between the control group and the experimental group.
Source: Gordis Epidemiology
What is the purpose of matching in case-control studies?
Matching ensures that cases and controls are comparable with respect to confounding factors.
Source: Principles of Epidemiology
What is a cross-sectional study?
A cross-sectional study examines data on exposure and outcome at a single point in time.
Source: Merck Veterinary Manual
What is a propagating epidemic?
A propagating epidemic is characterized by person-to-person transmission, resulting in a series of progressively taller peaks in cases.
Source: Gordis Epidemiology
If a town reports 50 new cases of a disease in a population of 5,000 during a single month, what is the incidence rate?
The incidence rate is 50/5,000 = 1%, or 10 cases per 1,000 population per month.
Source: Principles of Epidemiology
A study finds that smokers have a lung cancer risk 10 times higher than non-smokers. What measure does this ratio represent?
This represents the relative risk of lung cancer among smokers compared to non-smokers.
Source: Gordis Epidemiology
In a recent outbreak, most cases occurred within 24 hours of a wedding banquet. What type of epidemic does this suggest?
This suggests a point-source epidemic, where all cases result from a single exposure event.
Source: Principles of Epidemiology
What if a diagnostic test has a sensitivity of 90%? What does this mean for disease detection?
A sensitivity of 90% means the test correctly identifies 90% of individuals with the disease, but 10% may be false negatives.
Source: Merck Veterinary Manual
If a screening program detects many asymptomatic cases of a disease, what type of bias might this introduce?
This could introduce length-time bias, as slower-progressing cases are more likely to be detected.
Source: Gordis Epidemiology
During an outbreak, 20 cases are reported in a group of 100 exposed people. What is the attack rate?
The attack rate is 20/100 = 20%.
Source: Principles of Epidemiology
If an odds ratio is calculated as 2.5 in a case-control study, what does this indicate?
An odds ratio of 2.5 indicates that the odds of exposure are 2.5 times higher in cases than in controls.
Source: Gordis Epidemiology
A vaccine trial shows a relative risk reduction of 80%. What does this imply?
An 80% relative risk reduction means that the vaccinated group has 80% fewer cases compared to the unvaccinated group.
Source: Principles of Epidemiology
If a disease is highly prevalent but has low incidence, what does this suggest about its nature?
This suggests the disease is chronic, with many existing cases but few new cases developing over time.
Source: Merck Veterinary Manual
What if a p-value is reported as 0.03? How should this result be interpreted?
A p-value of 0.03 indicates a 3% probability that the observed results occurred by chance, often considered statistically significant.
Source: Gordis Epidemiology
What if an epidemic curve shows multiple peaks? What could this indicate?
Multiple peaks in an epidemic curve often indicate a propagating epidemic with person-to-person transmission.
Source: Principles of Epidemiology
If a test has a specificity of 95%, what does this mean for non-disease detection?
A specificity of 95% means the test correctly identifies 95% of people without the disease, with a 5% false-positive rate.
Source: Merck Veterinary Manual
A city implements a flu vaccine program, and the incidence of flu decreases significantly. What is this an example of?
This is an example of primary prevention, reducing the occurrence of disease through vaccination.
Source: Gordis Epidemiology
What if a study finds a relative risk of 1.0 between two groups? What does this imply?
A relative risk of 1.0 implies there is no difference in risk between the two groups.
Source: Principles of Epidemiology
If a population has high herd immunity, what would you expect to happen to disease transmission?
High herd immunity reduces disease transmission, as there are fewer susceptible individuals for the pathogen to infect.
Source: CDC Principles of Epidemiology
A study reports a confidence interval of 1.5 to 3.0 for an odds ratio. What does this mean?
This indicates that the true odds ratio is likely between 1.5 and 3.0, with a given confidence level (e.g., 95%).
Source: Gordis Epidemiology
If a screening test detects more cases in one population than another, what factors could explain this?
Factors could include differences in disease prevalence, access to healthcare, or the sensitivity and specificity of the test.
Source: Principles of Epidemiology
If a disease has an incubation period of 2-4 days, what does this suggest about its control measures?
Control measures need to be rapid to identify and isolate cases before they become infectious.
Source: Merck Veterinary Manual
What if a new diagnostic test identifies all cases but also many false positives? How could this impact its use?
The test has high sensitivity but low specificity, leading to overdiagnosis and possibly unnecessary treatments.
Source: Gordis Epidemiology
A researcher notes that areas with more hospitals have higher mortality rates. What type of bias could explain this?
This could be an example of ecological fallacy, assuming a group-level association applies to individuals.
Source: Principles of Epidemiology
What if an outbreak investigation identifies a food item as the source of infection? What should happen next?
The food item should be recalled, and public warnings issued to prevent further exposure.
Source: CDC Principles of Epidemiology
If a vaccine has an efficacy of 70%, what does this mean?
Vaccine efficacy of 70% means a 70% reduction in disease incidence among the vaccinated group compared to the unvaccinated group.
Source: Gordis Epidemiology
If a disease cluster is identified in a workplace, what steps should investigators take?
Investigators should define cases, collect exposure histories, and test hypotheses about the source and transmission route.
Source: Principles of Epidemiology
What if a study only recruits participants from hospitals? What type of bias might occur?
This could result in selection bias, as hospital patients may not represent the general population.
Source: Merck Veterinary Manual
What if a screening test for cancer improves survival time without reducing mortality? What bias might this indicate?
This suggests lead-time bias, where early detection does not change the natural history of the disease.
Source: Gordis Epidemiology
A rural village reports a sudden spike in diarrheal disease after a festival. What type of epidemic does this suggest?
This suggests a point-source epidemic, likely linked to contaminated food or water at the festival.
Source: Principles of Epidemiology
What if a study’s confidence interval for an odds ratio includes 1.0? How should this result be interpreted?
If the confidence interval includes 1.0, the result is not statistically significant, as the null hypothesis cannot be rejected.
Source: Merck Veterinary Manual
If a disease has a high basic reproductive number (R0), what does this imply about its spread?
A high R0 indicates the disease is highly transmissible and likely to spread widely without intervention.
Source: Gordis Epidemiology
If a study finds a new intervention significantly reduces mortality, what should researchers consider next?
Researchers should evaluate the intervention’s feasibility, cost-effectiveness, and potential side effects before widespread implementation.
Source: Principles of Epidemiology
If a disease is endemic in a region, what does this mean about its occurrence?
An endemic disease is consistently present in a population or region, often at predictable levels.
Source: CDC Principles of Epidemiology