COVID-19 definitions

Active cases

The number of confirmed cases minus the number of recovered cases and deaths. It is the number of cases still considered to be infectious.

Close contact

A person who has had face-to-face contact OR shared a close space, for any amount of duration, with someone who has been diagnosed with COVID-19 (while they were considered infectious).

A person who has been in an area where there is a high prevalence of COVID-19 infection or has been in a venue when COVID-19 transmission was occurring.

Community transmission

People who have tested positive for COVID-19 where the source is unknown, presumably someone in the local community.

Contact tracing

The process of talking to people who have been diagnosed with COVID-19 to determine who they have had close contact with.

This is to identify who is at risk of catching the disease from the case. Every person identified as a close-contact will be notified of their risk of acquiring the disease and will be informed of their need to self-quarantine for 14 days.


CovidSafe App (external site) is an Australian Government mobile phone app that helps state and territory health officials to quickly identify and contact people who may have been exposed to COVID-19 (called ‘close contacts’).

In many cases, people won't know the names and contact details of everyone they’ve been in close contact with (for example, on public transport).


Epidemiology means ‘the study of people’ and looks at the who, where and when (people, place and time) of a disease.

Good hygiene

Things you can do to protect your health and prevent the spread of germs to others, including:

  • washing your hands often with soap and water or an alcohol-based hand sanitiser
  • coughing and sneezing into your inner elbow
  • staying at home if you’re sick
  • regularly cleaning frequently touched surfaces.


An outbreak is the occurrence of more cases of disease than would normally be expected in a specific place or group of people over a given period of time.

As COVID-19 is a new disease, the term ‘outbreak’ is further defined in terms of the setting in which the case(s) occur and the potential for rapid transmission.

Physical distancing

Staying a safe distance from others to prevent the spread of the virus.

This includes:

  • staying at least 1.5 metres from others
  • avoiding physical greetings such as handshakes, hugs and kisses.


This refers to people who tested positive to COVID-19 or who have symptoms and have undergone a COVID-19 test and are waiting on results.

These people need to stay in their home, hotel or other accommodation until they receive their test results, or if they have tested positive, until they are cleared by the Public Health Unit.


People who are at greater risk of having COVID-19 (e.g. they may have had close contact with someone who is unwell with COVID-19 or just returned from overseas) need to remain in their home, hotel room or other accommodation for 14 days.


A physical feature which suggests that you may have COVID-19 such as a cough, fever, shortness of breath, sore throat, runny nose or loss of smell or taste.


Medical tests to find out if a person has a disease.

Testing at the time of infection

Testing for COVID-19 at the time of the infection is by taking nose and throat swabs. These are then sent to the laboratory for testing.

Asymptomatic testing

When a person is tested for a disease without having any symptoms of the disease (such as a fever, cough or shortness of breath). Asymptomatic testing for COVID-19 is only permitted under certain circumstances.

Serology testing

Serology testing is testing of a blood sample to measure antibodies to a disease. People develop antibodies as part of an immune response to a virus. Antibodies take time to develop (from days to weeks) and so serology testing cannot be relied on to diagnose an active infection. It can be used under certain circumstances for the diagnosis of a past COVID-19 infection.

Last reviewed: 27-01-2021

This publication is provided for education and information purposes only. It is not a substitute for professional advice. Information about a service, product or treatment does not imply endorsement and is not intended to replace professional advice. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified professional for answers to their questions.

Coronavirus information helplines: 13 COVID (13 268 43). Interstate callers: 1800 595 206. International callers: +61 8 9118 3100.