Epidemiology of Infectious Diseases – Key Vocabulary

75 vocabulary flashcards covering foundational concepts, historical figures, metrics, study designs, infection control, vaccinology, and global health topics in the epidemiology of infectious diseases.

Epidemiology

Branch of medicine that studies patterns, causes, and effects of health and disease conditions in defined populations.

Five W’s of Epidemiology

Core questions—Who, What, Where, When, and Why—used to characterize disease events in populations.

Public Health

Community-wide practices aimed at preventing disease, prolonging life, and promoting health through organized efforts.

Centers for Disease Control and Prevention (CDC)

U.S. federal agency responsible for protecting public health through disease control, surveillance, and prevention.

Public Health Service (PHS)

Umbrella organization within the U.S. government that oversees national public health activities, including the CDC.

Florence Nightingale

Pioneer nurse who used statistics during the Crimean War to cut soldier mortality and launch modern epidemiology.

John Snow

Physician who traced London’s 1854 cholera outbreak to a contaminated water pump, earning the title ‘father of field epidemiology.’

Epidemic Intelligence Service (EIS)

Rapid-response division of the CDC that deploys scientists worldwide to investigate disease outbreaks.

Incidence

Number of new cases of a disease occurring in a population during a specified period of time.

Prevalence

Total number of existing disease cases (new and pre-existing) in a population at a given time.

Mortality Rate

Proportion of deaths in a population attributable to a particular disease over a specified period.

Point-Source Epidemic

Outbreak in which all cases are exposed to the infectious agent at the same time from a single source.

Common-Source Epidemic

Epidemic due to exposure to a single source that persists over time, causing cases over an extended period.

Propagated Epidemic

Outbreak spread person-to-person, resulting in successive waves of transmission (e.g., influenza).

Index Case

First documented patient in an epidemiologic investigation of a disease outbreak.

Endemic Disease

Illness that maintains a relatively steady, predictable rate in a particular geographic area.

Sporadic Disease

Disease that appears irregularly and infrequently in random locations.

Epidemic

Occurrence of disease cases in excess of normal expectancy within a population or region.

Pandemic

Epidemic that spreads across multiple countries or continents, affecting a large number of people.

Natural History of Disease

Full progression of a disease in the host, from susceptibility through subclinical and clinical stages to outcome.

Susceptible Host Stage

Period before exposure when an individual is vulnerable but not yet infected.

Subclinical Disease Stage

Interval after exposure when pathological changes occur without observable symptoms.

Clinical Disease Stage

Phase in which signs and symptoms are evident; ends in recovery, disability, or death.

Screening Test

Low-cost, noninvasive test performed on asymptomatic populations to detect potential disease early.

Diagnostic Test

More precise, often invasive assessment used to confirm or rule out a disease in symptomatic or screen-positive individuals.

Specificity

Ability of a test to correctly identify those who do NOT have the disease (low false-positive rate).

Sensitivity

Ability of a test to correctly identify those who DO have the disease (low false-negative rate).

False Positive

Test result that incorrectly indicates the presence of a disease in a healthy individual.

False Negative

Test result that fails to detect a disease that is actually present in the individual.

Correlation

Statistical relationship between two variables that move together but do not necessarily imply cause and effect.

Causation

Situation in which exposure to a factor directly produces a specific outcome or disease.

Randomized Controlled Trial (RCT)

Experimental study design that randomly assigns participants to receive an intervention or control to assess causal effects.

Cross-Sectional Study

Observational study that measures exposure and disease status simultaneously at one point in time.

Case–Control Study

Retrospective study comparing exposures in people with a disease (cases) to those without (controls).

Cohort Study

Prospective or retrospective study following a disease-free population over time to see who develops the outcome in relation to exposures.

Hill’s Criteria

Set of guidelines (e.g., strength, consistency, temporality) used to infer causality from observational data.

Strength of Association

Magnitude of the relationship between exposure and outcome; stronger links support causality.

Consistency of Association

Observation that different studies yield similar findings regarding an exposure-disease link.

Specificity of Association

Criterion stating that an exposure leads to a single disease or a disease is linked to one exposure.

Temporality (Hill)

Requirement that the cause precedes the effect in time to support a causal inference.

Biological Plausibility

Existence of a scientifically reasonable mechanism explaining how an exposure could cause an outcome.

Surveillance

Ongoing systematic collection, analysis, and dissemination of health data for disease prevention and control.

Notifiable Disease

Condition that must be reported by law to public health authorities because of its public health importance.

Morbidity and Mortality Weekly Report (MMWR)

CDC’s weekly bulletin summarizing U.S. data on reportable diseases and health topics.

Healthcare-Associated Infection (HAI)

Infection acquired during the course of receiving treatment for other conditions in a healthcare facility.

Catheter-Associated Urinary Tract Infection (CAUTI)

UTI developing in a patient with an indwelling urinary catheter.

Central Line-Associated Bloodstream Infection (CLABSI)

Serious bloodstream infection linked to a central venous catheter.

Surgical Site Infection (SSI)

Infection occurring at or near a surgical incision within 30 days of a procedure.

Ventilator-Associated Event (VAE)

Range of complications, including pneumonia, occurring in patients on mechanical ventilation.

Medical Asepsis

Procedures, such as handwashing and disinfection, that reduce the number and spread of pathogens.

Surgical Asepsis

Strict sterile techniques used during invasive procedures to eliminate all microorganisms.

Infection Control Officer

Hospital professional who monitors, educates, and enforces practices to prevent HAIs.

Basic Reproduction Number (R0)

Average number of secondary infections produced by one case in a fully susceptible population.

Effective Reproduction Number (Rt)

Actual average number of secondary cases at a given time, accounting for immunity and interventions.

Case Fatality Rate (CFR)

Proportion of individuals with a disease who die from it, usually expressed as a percentage.

Herd Immunity

Indirect protection from infection conferred when a high proportion of a population is immune.

Phase I Clinical Trial

Initial testing of a vaccine or drug in 20-100 healthy volunteers to assess safety and dosage.

Phase II Clinical Trial

Study in several hundred participants to further evaluate safety and immunogenicity or efficacy.

Phase III Clinical Trial

Large-scale study in thousands of people to confirm efficacy and monitor common side effects before licensing.

Emergency Use Authorization (EUA)

FDA mechanism permitting use of unapproved medical products during public health emergencies.

Vaccine Adverse Event Reporting System (VAERS)

U.S. passive surveillance system for collecting reports of adverse events after vaccination.

Vaccine Injury Compensation Program (VICP)

Federal program that provides financial compensation for vaccine-related injuries, even without proven causation.

Emerging Disease

Infection caused by a newly identified or evolved pathogen increasing in incidence or geographic range.

Reemerging Disease

Previously controlled or declining disease that is again becoming significant due to factors like travel or resistance.

Global Disease Detection (GDD) Service

CDC-WHO partnership that monitors and responds to emerging global health threats.

Neglected Parasitic Infection (NPI)

Parasitic disease common in impoverished U.S. populations that receives limited public health attention.

Chagas Disease

NPI caused by Trypanosoma cruzi, leading to chronic heart and digestive complications.

Neurocysticercosis

Brain infection by Taenia solium larvae, a major cause of seizures worldwide.

Toxocariasis

Tissue-migrating worm infection that can damage the eye and other organs.

Toxoplasmosis

Protozoan infection often mild but dangerous to fetuses and immunocompromised individuals; affects ~60 million Americans.

Trichomoniasis

Sexually transmitted protozoal infection that increases susceptibility to other STIs and preterm birth risk.

Bioterrorism

Intentional release or threat of pathogens or toxins to cause illness or death in people, animals, or plants.

Agroterrorism

Use of biological agents to disrupt or destroy the agricultural sector and food supply.

Antibiotic Resistance

Ability of microbes to withstand drugs that once killed them, complicating infectious disease control.

World Health Organization (WHO)

United Nations agency coordinating international public health efforts and disease surveillance.