A COVID-19 glossary: What the terms mean and some subtle differences


Confused about the language that health and government officials are using during this COVID-19 pandemic?

Below is our glossary for terms currently in circulation as officials strive to keep people informed.

Community transmission

When referring to how a disease is spread, one of the methods is community transmission.

In the case of COVID-19, it means that an infected person has not come into known contact with anyone who is infected and that the source of infection is unknown.

Contact tracing

Contact tracing is what doctors use to track a virus's spread. It involves three steps.

First, is contact identification. Once a person is infected and symptomatic with a disease, the person is asked about their activities and their interactions with others.

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That's followed by contact listing. Once contacts with the infected person are identified, they're informed of their status and advised to get early care if they begin to develop symptoms. If they are considered high risk, they may also be advised to isolate themselves.

Finally, there is contact follow-up, where doctors get in touch with people who came into contact with the infected person to see if they begin to develop symptoms.

Coronavirus, COVID-19 and SARS-CoV-2

Coronaviruses are a common cause of colds and other upper respiratory infections, but this pandemic involves a strain of coronavirus that is new to the world's human population.

Coronavirus is used as a kind of shorthand these days in some media reports, and the new strain is more accurately called the novel coronavirus. The illness caused by the virus is called COVID-19, also referred to by the World Health Organization (WHO) as coronavirus disease 2019.

Some articles in medical journals use a lesser-known term for the virus: SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2).

The WHO says it's avoiding that term, since it could be confused with the SARS outbreak in 2003.

Endemic, epidemic and pandemic

A disease that is endemic is one that re-emerges on a seasonal basis, occurring at a predictable rate in a certain area or among a set population, such as malaria.

Epidemic is used when the number of infections rises above what is normally expected in a certain population or region. An outbreak is basically the same thing as an epidemic, although the term is often used to cover a more limited geographic area, according to the Centers for Disease Control and Prevention (CDC).  

Pandemic relates to the geographic spread of a disease. The WHO designated COVID-19 as a pandemic on March 11, citing the spread of the new virus to several countries.


A city or country where an outbreak is most pronounced.

Flattening the curve

Flattening the curve refers to a graph that illustrates the spread of a disease and the ability of health systems to cope.

If a large number of people become infected and require medical care, it can overwhelm the overall health-care system. This can result in shortages of protective equipment, hospital beds or even doctors and nurses.

On the graph, it's represented as a steep curve. 

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If adequate measures are taken to avoid the spread of infection and fewer patients require medical care, the curve on the graph isn't as sharp, and there would be a better chance that patients can receive the necessary care. This is referred to as "flattening the curve."

Nasopharyngeal vs. oropharyngeal swabs

To be tested for the virus, health-care professionals need to collect samples. This can be done one of two ways. 

A nasopharyngeal swab can look like an extra-long Q-Tip or a plastic wand with a collection surface on the end. It is inserted up the nose, far back where the health-care professional collects a sample by swabbing. This is the method preferred by the World Health Organization in testing for COVID-19.

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However, there is another method of collection available to health-care professionals: an oropharyngeal swab. Instead of going up a patient's nose, the sample is collected orally at the back of a patient's throat.


This is shorthand for personal protective equipment, and for health-care workers on the front line, it includes isolation gowns, foot covers, eye gear, face masks and gloves.


R0, pronounced "R-naught" is a measurement used to describe the intensity of an outbreak.

R0 is only used when everyone is vulnerable to a disease, meaning no one has had the disease before, and therefore has not been vaccinated. As a result, there is no way to control the spread. 

An R0 value of 1 means that each infection will cause one new infection. If it's greater than 1, each infection will cause more than one new infection. This could create a potential epidemic. 

The outbreak in China had an early R0 value estimate of 1.4 to 3.9

Presumptive and confirmed cases

A presumptive case means that a local health agency has received a positive test result from a patient. But the test needs to be validated with a second test. Some provincial labs, such as those in Ontario, British Columbia, Quebec and Alberta, conduct the second test whereas other provinces need to send a sample to the National Microbiology Lab in Winnipeg.

Once two tests have come back positive, it is a confirmed case.


An infection case is considered resolved when a person is no longer infected with the virus.

Self-isolation vs. quarantine vs. shelter-in-place


The terms are often used interchangeably. But health officials sometimes distinguish between "quarantine" and "isolation," which can be both voluntary and mandatory.

Self-isolation applies only to people who are known to be infected, according to some experts. Others use self-isolation as a synonym for quarantine. In both cases, those isolated need to stay at home and keep away from people who are not sick.

Watch: How does coronavirus quarantine work?

Quarantine describes separating and restricting the movement of people who may have been exposed to a contagious disease to see if they become sick. People who are quarantined could be healthy and are not necessarily infected.

Shelter-in-place is used in some parts of the U.S. and broadly means to quarantine. People are asked to stay at home with only limited exceptions, such as briefly shopping for essentials or going outside for exercise while still staying away from others.

Social distancing versus physical distancing

The World Health Organization stressed on March 25 that it is no longer using "social distancing" in its updates. It now prefers the term "physical distancing" to remind people to stay in touch with the elderly and other vulnerable groups.

The terms are interchangeable, and according to top health experts, distancing means keeping at least two metres away from others.

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