COVID-19 Australia: Epidemiology Report 71 Reporting period ending 12 February 2023

Four-week reporting period (16 January 2023 - 12 February 2023) Case definitions for confirmed and probable cases are in accordance with the coronavirus disease 2019 (COVID-19) Series of National Guidelines for Public Health Units (SoNG). The Australian Capital Territory did not supply hospitalisation data from 12 November to 24 November 2022, due to technical reasons. Trends - A fourth Omicron wave of COVID-19 transmission began in late October 2022, driven by a combination of existing and newly emerging Omicron subvariants. Following the peak of this wave in mid-December 2022, case numbers have been decreasing nationally. In the four-week period 16 January - 12 February 2023, there were 26,423 confirmed and 51,295 probable cases of COVID-19 reported in Australia to the National Notifiable Diseases Surveillance System (NNDSS). In the most recent reporting fortnight, a total of 35,509 confirmed and probable cases were notified (an average of 2,536 cases per day), compared to 42,209 in the previous fortnight (an average of 3,015 cases per day). Age group - Since late December 2022, notification rates have decreased across all age groups, with rates highest among adults aged 30 years and over. In the current reporting period 16 January - 12 February 2023, the highest notification rate was observed among adults aged 80 years and over whilst the lowest rates were among people aged 19 years or less. For the entire Omicron wave to date (15 December 2021 - 12 February 2023), the highest notification rate has been in adults aged 20 to 29 years. Aboriginal and Torres Strait Islander people - In the reporting period 16 January - 12 February 2023, there were 3,127 new cases notified in Aboriginal and Torres Strait Islander people. In the current Omicron wave (15 December 2021 - 12 February 2023) there have been 392,993 cases notified in Aboriginal and Torres Strait Islander people, representing 3.6% (392,993/10,779,420) of all cases in the Omicron wave to date. Severity - The overall crude case fatality rate in the current fourth Omicron wave is 0.32%, which is higher than third wave (0.21%). The current case fatality rate is likely overestimated due to changes in case ascertainment and underreporting of non-severe cases. Since the start of the pandemic to 12 February 2023, there have been 170 cases of paediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS) reported to PAEDS, including two in the current reporting period and two new cases in the previous reporting period. Virology - For samples collected in the four-week period 16 January - 12 February 2023, all 3,993 samples were assigned against Omicron or recombinants involving Omicron lineages. There is currently significant diversity in the range of sub- and sub-sub-lineages circulating within Australia. During the current reporting period more than 200 unique lineages have been identified. BA.2 and recombinant lineages made up similar proportions of sequences identified, with 40.1 % of sequences identified as BA.2 and 39.6% found to be recombinant lineage. The proportion of BA.5 and its sub lineages is slowly declining, constituting 19.3% of all lineages available for analysis in AusTrakka in the current reporting period. Of the Omicron sequences in AusTrakka to date, 19.9% are BA.1; 39.2% are BA. 2; <0.001% are BA.3; 3.8% are BA.4 and 32.2% are BA.5. All sub-lineages have been collapsed into respective major sub-lineages. Recombinants make up 4.9% of all Omicron sequences to date. International situation - According to the World Health Organization (WHO), cumulative global COVID-19 cases stood at over 755 million COVID-19 cases and over 6.8 million deaths as of 12 February 2023. For the South-East Asia and Western Pacific regions combined, there were 3,616,486 new cases and 32,380 deaths in the four-week period to 12 February 2023. Compared with the previous four-week reporting period, new cases and new deaths decreased in the Western Pacific region and the South-East Asia region. In total, since the start of the pandemic, over 261 million cases and over 1.2 million deaths have been reported in the two regions.