Glossary Terms
This glossary helps make complex public health and infectious disease terms easier to understand—for students, journalists, health professionals, policymakers, and anyone interested in these topics. As outbreaks and health threats grow more complex, so does the language used to describe them. I created this resource to provide concise, accurate definitions grounded in science and real-world experience. Whether you’re learning the basics or deepening your expertise, this glossary is here to support informed decision-making and better communication.
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Airborne Transmission
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The spread of infectious agents through aerosols that remain suspended in the air and can infect people over distances.
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Force of Infection (FOI)
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The rate at which susceptible individuals acquire an infection over time.
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Surveillance Systems
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Networks for collecting, analyzing, and interpreting health data to guide public health actions and evaluate interventions.
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Syndromic Surveillance
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Monitoring of symptoms or clinical features rather than confirmed diagnoses to detect outbreaks early.
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Pathogen-based Surveillance
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Monitoring specific infectious agents through laboratory testing and genetic analysis.
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Contact Tracing
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The process of identifying, assessing, and managing people who have been exposed to a disease to prevent further transmission.
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Passive Surveillance
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A system where healthcare providers report cases of notifiable diseases to public health authorities.
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Sentinel Surveillance
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A surveillance system that monitors disease trends using selected healthcare facilities.
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Active Surveillance
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A system where public health officials actively seek out cases through regular contact with healthcare providers.
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Droplet Transmission
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Infection spread via respiratory droplets expelled during coughing, sneezing, or talking. Term has now fallen out of favor, but should be referenced for historical purposes.
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Aerosol
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Tiny particles suspended in the air that can contain infectious agents and travel over longer distances than droplets.
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Direct Contact Transmission
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The spread of disease through physical contact between an infected person and a susceptible individual.
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Vector-borne Transmission
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The spread of pathogens by insects or other animals that transmit infectious agents from one host to another.
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Fomite
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An inanimate object that can be contaminated with infectious agents and serve as a vehicle for transmission.
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Basic Reproduction Number (R₀)
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The average number of secondary cases caused by one infected person in a fully susceptible population; measles has one of the highest R₀ values.
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Secondary Attack Rate
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The proportion of susceptible individuals who become infected after exposure to a contagious person.
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Infectious Period
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The time during which an infected individual can transmit the disease to others.
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Outbreak Investigation
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Case definitions, attack rates, reproductive number (R₀), superspreaders, source tracing.