- Carrier: A person or animal without apparent disease who harbors a specific infectious agent and is capable of transmitting the agent to others. The carrier state may occur in an individual with an infection that is inapparent throughout its course (known as asymptomatic carrier), or during the incubation period, convalescence and postconvalescence of an individual with a clinically recognizable disease. The carrier state may be of short or long duration (transient carrier or chronic carrier).
- Community Spread: Spread of an illness for which the source of infection is unknown.
- Chain of Infection: A process that begins when an agent leaves its reservoir or host through a portal of exit, and is conveyed by some mode of transmission, then enters through an appropriate portal of entry to infect a susceptible host.
- Direct Transmission: The immediate transfer of an agent from a reservoir to a susceptible host by direct contact or droplet spread.
- Epidemic: The occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time.
- Incubation Period: A period of subclinical or inapparent pathologic changes following exposure, ending with the onset of symptoms of infectious disease.
- Indirect Transmission: The transmission of an agent carried from a reservoir to a susceptible host by suspended air particles or by animate (vector) or inanimate (vehicle) intermediaries.
- Outbreak: Synonymous with epidemic. Sometimes the preferred word, as it may escape sensationalism associated with the word epidemic. Alternatively, a localized as opposed to generalized epidemic.
- Pandemic: An epidemic occurring over a very wide area (several countries or continents) and usually affecting a large proportion of the population.
- Presumptive Positive: A case that has tested positive by a public health laboratory and is pending confirmatory testing at CDC.
- Propagated Outbreak:An outbreak that does not have a common source, but instead spreads from person to person.
- Public Health Surveillance: The systematic collection, analysis, interpretation and dissemination of health data on an ongoing basis, to gain knowledge of the pattern of disease occurrence and potential in a community, in order to control and prevent disease in the community.
- Quarantine/Isolation: Isolation and quarantine help protect the public by preventing exposure to people who have or may have a contagious disease. Isolation separates sick people with a contagious disease from people who are not sick. Quarantine separates and restricts the movement of people who were exposed to a contagious disease to see if they become sick.
- Risk Factor: An aspect of personal behavior or lifestyle, an environmental exposure or an inborn or inherited characteristic that is associated with an increased occurrence of disease or other health-related event or condition.
- Transmission of Infection: Any mode or mechanism by which an infectious agent is spread through the environment or to another person.
For additional words and their definitions, please visit the CDC glossary.
Source: Centers for Disease Control and Prevention