Coronavirus (COVID-19) Outbreak Glossary

This resource provides a description of some key terms used in the current Coronavirus (COVID-19) outbreak.

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Showing no symptoms of disease. A person infected with the virus can be asymptomatic because they are in an early stage of infection and symptoms have not yet developed (“pre-symptomatic”), or they may not develop any symptoms at all during their infection.



The name of the disease caused by the novel coronavirus, SARS-CoV-2, and is short for “Coronavirus Disease 2019.” (Source: WHO)

Case fatality rate (CFR)

An estimate of the risk of mortality from a contagious disease. The CFR is calculated by dividing the number of deaths caused by a disease by the number of cases of that disease in a given time period. The CFR is time and location-dependent, and many different factors can influence the CFR, such as speed of diagnosis of cases, health system capacity, age and other demographic characteristics, among others. For COVID-19, estimates of the CFR have varied; in China, CFR estimates by province have ranged from <1% to 5.8%. (Sources: CDC/Lipsitch et. al./WHO)

Close contact

A person who may be at risk of a contagious disease because of their proximity or exposure to a known case. Exact definition of close contact differs by disease; for COVID-19, the CDC defines a close contact as anyone who has been within 6 feet of a person infected with the virus for a prolonged period of time, or has had direct contact with the infected person’s secretions. (Source: CDC)

Community transmission/spread

Infections identified in a given geographic area without a history of travel elsewhere and no connection to a known case.

Contact tracing

The process of identifying, assessing, and managing people who have been exposed to a contagious disease to prevent onward transmission. (Source: WHO)

Cordon sanitaire

A measure preventing anyone from leaving a defined geographic area, such as a community, region, or country infected by a disease to stop the spread of the disease.


A family of viruses that cause illness ranging from the common cold to more severe diseases, such as Middle East Respiratory Syndrome (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS-CoV). The novel coronavirus recently discovered has been named SARS-CoV-2 and it causes COVID-19. (Source: WHO)


Drive through testing

Individuals remain in their vehicles, and medical staff in protective gear come to administer the swab test and the swabs are sent to a laboratory for testing.

Droplet transmission/spread

A mode of transmission for a contagious disease that involves relatively large, short-range (less than 6 feet) respiratory droplets produced by sneezing, coughing, or talking. (Source: CDC)


Elective surgeries

Procedures that are considered non-urgent and non-essential. During periods of community transmission, CDC is recommending postponing elective procedures, surgeries, and non-urgent outpatient visits. (Source: CDC)


An increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area. (Source: CDC)

Essential activities

  • Tasks essential to main health and safety, such as obtaining medicine or seeing a doctor;
  • Getting necessary services or supplies for themselves or their family or household members, such as getting food and supplies, pet food, and getting supplies necessary for staying at home;
  • Engaging in outdoor activity, such as walking, hiking or running provided that you maintain at least six feet of social distancing;
  • Performing work providing essential services at an Essential Business or Essential Government function;
  • Caring for a family member in another household;
  • Caring for elderly, minors, dependents, person with disabilities, or other vulnerable persons
  • Essential businesses: (Source:
  • Healthcare operations, including home health workers;
  • Essential Infrastructure, including construction of housing and operation of public transportation and utilities;
  • Grocery stores, farmers’ markets, food banks, convenience stores;
  • Businesses that provide necessities of life for economically disadvantaged individuals and shelter facilities;
  • Pharmacies, health care supply stores, and health care facilities;
  • Gas stations and auto repair facilities;
  • Banks;
  • Garbage collection;
  • Hardware stores, lumbers, electricians, and other service providers necessary to maintain the safety, sanitation, and essential operation of residences and other essential businesses;
  • Educational institutions, for the purposes of facilitating distance learning;
  • Laundromats, dry cleaners, and laundry service providers;
  • Businesses that ship or deliver groceries, food, and good directly to residences;
  • Childcare facilities providing services that enable essential employees to go to work;
  • Roles required for any Essential Business to “maintain basic operations,” which include security, payroll, and similar activities
(Source: Press Release from the Office of the Mayor: "San Francisco Issues New Public Health Order Requiring Residents Stay at Home Except for Essential Needs" March 16, 2020).

Essential government functions

All services needed to ensure the continuing operation of the government agencies and provide for the health, safety and welfare of the public. (Source: Press Release from the Office of the Mayor: "San Francisco Issues New Public Health Order Requiring Residents Stay at Home Except for Essential Needs" March 16, 2020).


Flattening the curve

Slowing a virus’ spread to reduce the peak number of cases and related demands on hospitals and infrastructure (Source: CDC)


An inanimate object that can be the vehicle for transmission of an infectious agent (e.g., bedding, towels, or surgical instruments). There is evidence that coronavirus spreads via fomites although, this is a less common route of transmission. (Source: CDC)


Home isolation

Persons with COVID-19 who have symptoms or laboratory-confirmed COVID-19 who have been directed to stay at home until they are recovered. (Source: CDC)



Separating sick people with a contagious disease from those who are not sick. (Source: CDC)


N95 respirator (face mask)

Personal protective equipment that is used to protect the wearer from airborne particles and from liquid contaminating the face (Source: American Thoracic Society)

Negative-pressure rooms

Rooms specifically designed for patients with contagious diseases that contain any circulating air in the room and prevent it from being released into any other part of the hospital.



An epidemic that has spread over several countries/continents, usually affecting a large number of people. (Source: CDC)



Separating and restricting the movement of people exposed (or potentially exposed) to a contagious disease. (Source: CDC)


R0 / reproductive rate

An epidemiologic metric used to describe the contagiousness or transmissibility of infectious agents, which is usually estimated with complex mathematical models developed using various sets of assumptions. It is an estimate of the average number of new cases of a disease that each case generates, at a given point in time. R0 estimates for the virus that causes COVID-19 are around 2 to 3, which is slightly higher than that for seasonal influenza (R0 ~1.2-1.3), but far lower than more contagious diseases such as measles (R0 ~12 - 18). (Source: The basic reproduction number (R0) of measles: a systematic review, The Lancet, July 27, 2017.)



The name of the novel coronavirus that causes COVID-19 disease. (Source: WHO)


Staying home and away from other people as much as possible after exposure.

Shelter in place

All residents must remain at their place of residence, except to conduct essential activities, essential businesses, and essential government functions. (Source: Press Release from the Office of the Mayor: "San Francisco Issues New Public Health Order Requiring Residents Stay at Home Except for Essential Needs" March 16, 2020).

Social distancing

Measures taken to reduce person-to-person contact in a given community, with a goal to stop or slow down the spread of a contagious disease. Measures can include working from home, closing offices and schools, canceling events, and avoiding public transportation. (Source: CIDRAP)


Showing symptoms of disease. The most common symptoms of Covid-19 include: cough, shortness of breath or difficulty breathing, fever, chills, muscle pain, sore throat, and new loss of taste or smell.



A device that delivers air into the lungs through a tube that is placed into the mouth or nose and down into the windpipe. (Source: American Thoracic Society)

Viral shedding

The period of time after the virus has replicated in the host and is being emitted.

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