An A to Z glossary of the new coronavirus words

Dr Tajalli Saghaie
12 May 2020
Faculty of Medicine and Health Sciences


A new COVID-19 lexicon has emerged during the pandemic, passing from the lips of medicos into everyday conversation.

Since the spread of the coronavirus beyond China early this year, through the lockdown of Australia and now a cautious reopening, a range of words and phrases have newly entered into common useage.

Once the province of scientists and medicos, lingo such as ‘herd immunity’ and ‘flattening the curve’ has extended from labs and hospitals into suburban homes.

Given the pandemic has altered daily life beyond recognition, it’s little wonder we bandy about words such as ‘zoonotic’ and ‘co-morbidity’ as though we’re experts.

But the reality is, most of us are not experts, so to ensure we truly know what we’re talking about in the age of coronavirus, Dr Tajalli Saghaie, a respiratory physician at MQ Health, provides an A to Z glossary of the words and phrases in our new vocabulary, including some of the stories behind them.


Asymptomatic refers to someone who has no symptoms or presentations of a disease.

COVID-19 v coronavirus

Coronavirus is a name given to a family of viruses that cause respiratory illness. One of their characteristics is a protein on their surface that, under the electron microscope, sticks out and gives them a look that resembles a crown, hence the name ‘corona’.

The idea of separating the sick from the healthy goes back to biblical times and is mentioned in the Book of Leviticus.

COVID-19 is the name given (by the World Health Organisation) to the disease caused by the new virus in the coronavirus family, officially named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), discovered in 2019.

Flatten the curve

This idea is based on the fact that by reducing the transmission rate in a community, a situation where active cases increase out of control ('a spike') and overwhelm the health system can be avoided.

A slower and more controlled rate of transmission in the community will lead to a more manageable number of active cases and create the look on a graph of a flattened curve instead of a spike.

This may be achieved by a variety of strategies such as social distancing, a high volume of testing, contact tracing and restrictions in the community.

Herd immunity

Herd immunity refers to a situation where a large percentage of a population has become immune to a certain disease. This will significantly reduce the chance of an outbreak in that population as any active case is not likely to infect a significant number of others.

Morbidity and co-morbidity

'Morbidity' comes from the Latin word morbidus, meaning sick or unhealthy. In medicine it refers to any disease state that has a significant impact on a person's health. Co-morbidty is the simultaneous presence of different health conditions.

Novel coronavirus

'Novel' means new and refers to the fact that this virus has only recently been discovered.

Pandemic v epidemic

An ‘outbreak’ is a disease that is spreading on a small scale. When an outbreak continues to spread at a rapid rate involving large communities then it's called an ‘epidemic’. The situation escalates to a 'pandemic' when it continues to spread out of control at a larger scale (across countries and continents) and becomes prevalent around the world.

As the terminology has become a political term and not just a scientific one, the definitions and the difference between an epidemic and a pandemic are not crystal clear. WHO describes pandemic as the ‘worldwide spread of a new disease’.


The idea of separating the sick from the healthy goes back to biblical times and is mentioned in the Book of Leviticus in regards to leprosy.

Later, in the 14th century, the Venetians – inspired by the earlier Middle Eastern physicians and their texts – adopted the practice of docking all merchant ships for a period of 40 days before allowing disembarkation.

The practice was referred to as ‘quarantina’, which literally means 40 days.


A vaccine is a substance used to boost a person's immune system against a particular condition, without giving them the actual disease.

Originating from the Latin word meaning ‘derived from cows’, it refers to the origin story of all modern vaccines: in the late 18th century, English physician Edward Jenner demonstrated that children who were inoculated by cowpox pus were immune to smallpox.


A zoonotic infection is a disease that already exists in animals but can also infect humans. There are many examples of this in medicine, including rabies, anthrax and Ebola.

Dr Tajalli Saghaie is a respiratory physician and researcher in the MQ Health Respiratory and Sleep Clinic at Macquarie University Hospital.


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