State

Confounding

A situation where an external factor is associated with both the exposure and outcome, which may distort the true relationship between them.

Epi curve

A graphical representation of the frequency of cases of a disease over time.

Conditional probability

The likelihood of an event occurring given that another event has already occurred.

Relative risk

The ratio of the risk of an event occurring in the exposed group compared to the unexposed group.

Attribute risk

The difference in the incidence of a disease between an exposed group and an unexposed group.

Attributable fraction

The proportion of a disease in a population that can be attributed to a specific risk factor.

Descriptive epidemiology

The study of the distribution and patterns of health-related conditions in populations.

Analytical epidemiology

The study of determinants of health-related states and diseases, often involving comparisons of different groups.

Determinants

Factors that influence the occurrence and distribution of health-related conditions.

Quantification

The process of measuring or counting the occurrence of health-related events or conditions.

Carrier

An individual who harbors a disease-causing organism but does not show symptoms of the disease.

Etiological agent

The biological agent responsible for causing a disease.

Reservoir

The natural habitat where an infectious agent lives, grows, and multiplies.

Vector

An organism that transmits a pathogen to a host.

Vehicle

An inanimate object or substance that indirectly transmits a pathogen to a host.

Direct horizontal transmission

The spread of a disease directly from one individual to another, without an intermediary.

Direct vertical transmission

The transmission of a disease from a parent to offspring, usually through childbirth or breastfeeding.

Case fatality rate (CFR)

The proportion of individuals with a particular disease who die from that disease.

CFR formula

CFR = (Number of deaths from a disease / Number of diagnosed cases of that disease) × 100.

Rate difference formula

Rate Difference = (Rate in exposed group) - (Rate in unexposed group).

Relative risk formula

Relative risk = (Incidence rate in exposed group) / (Incidence rate in unexposed group).

Incidence formula

Incidence = (Number of new cases) / (Population at risk).

Disease transmission

The process by which a disease spreads from one individual to another or through an environment.

Contingency table

A matrix used to organize and analyze categorical data, especially for the comparison of different groups.

Risk factor

Any attribute, characteristic, or exposure that increases the likelihood of developing a disease or health condition.

Field investigation

A process where epidemiologists go into the field to study an outbreak and collect data to understand its cause.

Shoe leather epidemiology

The process of gathering data through direct investigation and contact, often by walking through affected areas.

Formative evaluation

Evaluation done during the development of a program to assess its feasibility and potential effectiveness.

Process evaluation

Evaluation that focuses on how a program is implemented, rather than its outcomes.

Summative evaluation

Evaluation conducted after a program has been implemented to assess its impact and effectiveness.

Linkages

The connections between various factors or organizations that can influence health outcomes.

Secular trends

Long-term patterns or trends in disease occurrence over time.

Experimental study

A study where the researcher actively manipulates an independent variable to observe its effect on a dependent variable.

Cohort study

A type of study that follows a group of people over time to examine how exposures affect the incidence of outcomes.

Prospective cohort study

A cohort study where participants are followed forward in time to see if they develop an outcome.

Retrospective cohort study

A cohort study that looks backward in time, using existing records to investigate exposures and outcomes.

Case-control study

A study that compares individuals with a disease (cases) to those without (controls) to identify potential risk factors.

Case-patient

A person who has been diagnosed with a particular disease during an outbreak or investigation.

Cross-sectional study

A study that examines a population at a single point in time to assess the prevalence of health conditions.

Epidemiological triad

A model describing the interaction between the agent, host, and environment in disease causation.

Agent

The microorganism or factor that causes disease.

Environment

The external factors (physical, social, or economic) that influence the spread and development of disease.

Causal pie

A model representing multiple factors (or 'slices') that contribute to the development of a disease.

Necessary cause

A factor that must be present for a disease to occur but is not sufficient by itself to cause the disease.

Spectrum of a disease

The range of manifestations and severity of a disease from mild to severe.

Indirect transmission

The spread of disease through a vector or vehicle rather than direct contact.

Hyperendemic

A situation where a disease is consistently present in a population at a higher-than-expected level.

Outbreak

A sudden increase in the number of cases of a disease above what is normally expected.

Cluster

A group of cases of a particular disease that occur in a specific time or place, but not necessarily in excess of what is expected.

Common source outbreak

An outbreak in which all affected individuals are exposed to a common source of infection.

Point source outbreak

A common source outbreak where the exposure occurs over a brief period of time.

Continuous common source outbreak

An outbreak where the exposure occurs over an extended period, often linked to a single source.

Intermittent common source outbreak

A common source outbreak where exposure occurs in waves, with periods of exposure followed by periods of no exposure.

Propagated outbreak

An outbreak that spreads from person to person, often with multiple waves of infection.

Mixed epidemic

An outbreak that involves both a common source and propagated transmission.

Public health surveillance

The continuous, systematic collection, analysis, and interpretation of health-related data for planning, implementation, and evaluation of public health practices.

Variable

Any factor, trait, or condition that can vary or change across a population.

Attack rate

The proportion of people who become ill after exposure to a specific risk factor or event.

Prevalence rate

The proportion of individuals in a population who have a specific disease at a particular point in time.

Secondary attack rate

The proportion of exposed individuals who become ill during an outbreak.

Point prevalence

The proportion of individuals with a disease at a specific point in time.

Period prevalence

The proportion of individuals with a disease during a specified period.

Proportionate mortality rate

The proportion of deaths in a population that are attributable to a specific cause.

Years of potential life lost

A measure of premature mortality that estimates the number of years lost due to early death.

Measures of association

Statistical measures, such as relative risk or odds ratio, that describe the relationship between an exposure and an outcome.

Null hypothesis

The hypothesis that there is no effect or association between the variables being studied.

Alternative hypothesis

The hypothesis that there is an effect or association between the variables being studied.

Subclinical

A stage of a disease in which symptoms are not yet noticeable but the disease is still present.

Temporality

The concept that an exposure must precede an outcome in order to establish a causal relationship.

Bayes Theorem

A mathematical formula used to update the probability of a hypothesis based on new evidence.

Dose response

A relationship between the dose of an exposure and the magnitude of the response or outcome.

Molecular epidemiology

The study of the role of genetic and molecular factors in disease patterns and causes.

Genetic epidemiology

The study of genetic factors in the occurrence and distribution of diseases in populations.

Smallpox

A contagious and deadly disease caused by the variola virus, eradicated through vaccination.

Minamata disease

A neurological disease caused by mercury poisoning, resulting from industrial pollution in Minamata Bay, Japan.

Proportional mortality

The proportion of deaths in a population attributed to a specific cause.

Impairment

A loss of function or ability in an individual, often due to disease or injury.

Disability

A physical or mental condition that limits a person's ability to perform daily activities.

Handicap

A disadvantage experienced by an individual due to a disability, often related to social or environmental factors.

Health indicator

A measure used to assess the health status of a population, such as mortality rates or life expectancy.

Ecological study

A study that looks at the relationships between exposure and disease at the population level, rather than the individual level.

Thalidomide

A drug that caused birth defects when used by pregnant women, leading to its withdrawal from the market.

Field trials

Studies conducted in real-world settings to evaluate the effectiveness of interventions.

Random error

The variation in results due to chance, not systematic bias.

Selection bias

A bias that occurs when the selection of participants in a study is not random, leading to an unrepresentative sample.

Healthy worker bias

A bias that occurs when the study population consists of workers, who may be healthier than the general population.

Measurement bias

A bias that occurs when there is an error in how data is collected or measured.

Recall bias

A bias that occurs when individuals with a disease or condition remember their exposures differently from those without the disease.

Validity

The extent to which a study accurately measures what it intends to measure.

Infectious disease

A disease caused by microorganisms like bacteria, viruses, fungi, or parasites.

Bacteria

Single-celled microorganisms that can cause diseases such as tuberculosis or pneumonia.

Viruses

Tiny infectious agents that require a host cell to reproduce and can cause diseases like the flu or COVID-19.

Fungi

Eukaryotic organisms that can cause diseases like athlete’s foot or candidiasis.

Protozoa

Single-celled organisms that can cause diseases such as malaria or giardiasis.

Helminths

Parasitic worms that cause diseases such as schistosomiasis or tapeworm infections.

Prions

Infectious proteins that cause neurodegenerative diseases, like Creutzfeldt-Jakob disease.

Nonspecific mechanisms

General defense mechanisms, like physical barriers or inflammation, that the body uses against all pathogens.

Specific mechanisms

Immune responses that target specific pathogens, like antibody production.

Threshold proportion

The proportion of individuals in a population who must be immune for herd immunity to prevent the spread of a disease.

Plasmid

A small, circular piece of DNA in bacteria that can carry genes, including those for antibiotic resistance.