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Public Health Terminology


In public health, there are specific terms used to describe parts of a response to a disease outbreak like   coronavirus 2019 (COVID-19). These terms may differ from similar definitions used in non-public health settings.  Public health language focuses on how diseases spread and how people are kept safe that have or may have a contagious disease, like COVID-19.

What Is the Difference Between Isolation and Quarantine?

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. Isolation is usually voluntary, but in an emergency, officials have the authority to isolate people who are sick.
  • Quarantine separates and restricts the movement of people who were exposed to a contagious disease to see if they become sick.  Quarantined people may or may not become sick; but separating them from those who were never exposed helps prevent the spread of the disease. Quarantine can be voluntary, but in an emergency, officials have the authority to quarantine people who have been exposed to an infectious disease.

What is Community Spread?

Community spread means people have been infected with a contagious disease in an area, including some who are not sure how or where they became infected.

How easily a virus spreads from person-to-person can vary. Some viruses are highly contagious (spread easily), like measles, while other viruses do not spread as easily. Another factor is whether the spread is sustained, spreading continually without stopping.

The virus that causes COVID-19 seems to be spreading easily and sustainably in the community ("community spread") in some affected geographic areas.

What is Contact Tracing?

Contact tracing is finding everyone who comes in direct contact with a sick patient, in this case someone with a positive test of COVID-19. These individuals, known as contacts, are quarantined and watched for signs of illness for 14 days from the last day they came in contact with the sick patient. If the contact develops symptoms of COVID-19, they are immediately isolated, tested, provided care, and the cycle starts again – all of the new patient's contacts are found, quarantined and watched for 14 days. Contact tracing finds new cases quickly so they can be quarantine or isolated, stopping further spread of COVID-19.                  

What Is the Difference Between Containment and Mitigation?

Containment is a plan that public health officials use to stop the rapid spread of a contagious disease like COVID-19. This includes using contact tracing to find and isolate sick individuals and quarantine individuals that have been exposed to a disease. The goal of containment is to stop the spread from very specific areas and avoid a larger outbreak.  

When containment is no longer effective at controlling the spread of disease, public health officials use mitigation strategies to lessen the impact of the contagious disease. Some mitigation efforts include promoting more social distancing, limiting large gatherings at which the disease might spread, and potentially even closing schools or canceling sporting events.

Resources for More Information

For more information, visit

The latest information on the coronavirus in the U.S. and worldwide can be found on the CDC website.



Date created: 3/9/2020​