Definition of a COVID-19 diagnosis
There were many revisions made to the COVID-19 surveillance case definition over the period covered in this report (2020 to 2022). In this report, a ‘COVID-19 diagnosis’ refers to people with at least one COVID-19 notification reported to state and territory notifiable disease registers. It includes both confirmed and probable cases based on diagnosis using nucleic acid amplification testing (such as reverse transcription polymerase chain reaction) or Rapid Antigen Tests. Since 1 July 2024, only confirmed cases are reported to the National Notifiable Diseases Surveillance System (NNDSS) (Department of Health, Disability and Ageing 2024).
See Defining COVID-19 diagnoses for more information.
A range of public health and social measures were implemented to assist in containing the spread of COVID-19 during the first 2 years of the pandemic (the ‘pre-Omicron’ period), and case numbers during this time were relatively low.
The Omicron variant emerged in late 2021. It was more transmissible than previous variants, and its emergence coincided with the relaxation of a number of public health measures following attainment of high rates of vaccine coverage in the population (AIHW 2025). As a result, the number of COVID-19 cases increased rapidly from early 2022 (see Table A1 and Figure 2.1).
Figure 2.1 shows the number of men and women diagnosed with COVID-19 while living in residential aged care, by dementia status, between January 2020 and December 2022. Figure 2.2 shows these results as a percentage of all aged care residents.
