Infectious Disease Glossary
Plain-language definitions for recurring infectious disease and public-health terms used across the topic hubs, commentary posts, resource notes, and source cards.
Glossary terms
- Antimicrobial resistance
- Botulism
- Case definition
- Community immunity
- Contact tracing
- Epidemic
- False negative
- False positive
- Foodborne illness
- HIV
- Incubation period
- Infection control
- Infectious disease
- Infectious period
- Measles
- Outbreak
- Pandemic
- Pertussis
- Post-exposure prophylaxis
- Public health emergency
- Public health surveillance
- Respiratory transmission
- Test sensitivity
- Test specificity
- Tuberculosis
- Vaccine
- Vaccine effectiveness
- Zoonotic disease
Definitions
Antimicrobial resistance
A situation where bacteria, viruses, fungi, or parasites become harder to treat with medicines that once worked against them. This site discusses AMR as a public-health and systems issue.
Botulism
A serious illness caused by toxins produced by certain bacteria. Possible botulism is urgent and requires immediate medical or public-health attention, not website-based self-assessment.
Case definition
A set of criteria used to decide whether someone should be counted as a case for surveillance or investigation. Case definitions can change as evidence improves.
Community immunity
A situation where enough people in a population have protection that spread becomes less likely. The level needed varies by disease and setting.
Contact tracing
A public-health process for identifying and notifying people who may have been exposed to an infection. Specific methods depend on disease, setting, privacy rules, and public-health guidance.
Epidemic
A wider or more sustained increase in disease occurrence within a population or region. The term is context-dependent and should be read with attention to source and date.
False negative
A test result that indicates a condition or infection is not present when it actually is. False negatives can occur for several reasons, including timing and test performance.
False positive
A test result that indicates a condition or infection is present when it is not. False positives are one reason test results need clinical and public-health context.
Foodborne illness
Illness linked to contaminated food or beverages. Public-health investigations may use reports, interviews, lab testing, and supply-chain information.
HIV
Human immunodeficiency virus, a virus that affects the immune system. This site discusses HIV mainly through public-health infrastructure, prevention systems, and source pathways, not personal medical advice.
Incubation period
The time between exposure to an infectious agent and when symptoms may appear. Incubation periods vary and should not be used alone for personal medical decisions.
Infection control
Practices and systems used to reduce infection spread in health-care, congregate, school, workplace, and community settings.
Infectious disease
An illness caused by an organism or agent that can spread directly or indirectly through people, animals, food, water, environments, or vectors. Public-health pages focus on transmission, prevention systems, and response rather than personal diagnosis.
Infectious period
The time during which a person or animal can transmit an infectious agent to others. The period varies by disease and context.
Measles
A highly contagious vaccine-preventable viral disease. Measles content should be read with current official guidance and clinician input for personal decisions.
Outbreak
An increase in disease cases above what is normally expected in a place, setting, or population. Outbreak interpretation depends on time, location, case definition, and available evidence.
Pandemic
An epidemic that has spread across countries or regions. Pandemic preparedness includes surveillance, response planning, communication, laboratories, and policy capacity.
Pertussis
A vaccine-preventable respiratory disease also known as whooping cough. Personal vaccination or treatment questions should be handled through current official guidance and clinical care.
Post-exposure prophylaxis
A preventive medicine or intervention used after a possible exposure to reduce the chance of infection. This is a medical decision that requires qualified clinical or public-health guidance.
Public health emergency
A situation that can require coordinated public-health action because of a serious threat to population health. Legal definitions and powers vary by jurisdiction.
Public health surveillance
The ongoing collection, analysis, interpretation, and use of health information to detect problems and guide public-health action.
Respiratory transmission
Spread through particles or droplets released when people breathe, talk, cough, sneeze, or sing. Risk depends on pathogen, distance, ventilation, time, and setting.
Test sensitivity
How well a test identifies people who truly have the condition or infection being tested for. A highly sensitive test has fewer false negatives, but interpretation also depends on context.
Test specificity
How well a test identifies people who do not have the condition or infection being tested for. A highly specific test has fewer false positives, but results still need context.
Tuberculosis
An infectious disease caused by Mycobacterium tuberculosis. Public-health work around TB includes screening, diagnosis, treatment support, contact investigation, and program infrastructure.
Vaccine
A product designed to train the immune system to recognize a pathogen or toxin. Vaccine recommendations depend on age, health status, risk, timing, and official guidance.
Vaccine effectiveness
A measure of how well a vaccine performs in real-world conditions for a defined outcome and population. It is not the same as a personal guarantee.
Zoonotic disease
An infectious disease that can move between animals and people. Zoonotic threats connect human health, animal health, food systems, and environmental conditions.