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Background Health care workers are at increased risk of SARS-CoV-2 infection due to potential exposure to patients or staff in health care settings. Australian health care services and health care workers experienced intense pressure to prepare for and respond to SARS-CoV-2 infections. We summarise national data on health care worker infections and associated outbreaks during 2020. Methods We collected aggregated data on infected health care workers and outbreaks in health care facilities from all jurisdictions. Health care workers working solely in residential aged care and outbreaks in residential aged care facilities were excluded. Jurisdictions provided data on the number of health care setting outbreaks, confirmed cases, hospitalisation, source of infection, and health care worker role. We analysed data for two periods that aligned with two distinct peaks in the epidemic relative to 1 June 2020, referred to here as the first wave (23 January – 31 May 2020) and the second wave (1 June – 18 September 2020). Results Jurisdictions reported a total of 2,163 health care worker infections with SARS-CoV-2 during the surveillance period. Source of acquisition was known for 81.0% of cases (1,667/2,059). The majority of cases in the first wave were acquired overseas, shifting to locally-acquired cases in the second wave. The odds of infection in the second wave compared to the first wave were higher for nurses/midwives (odds ratio, OR: 1.61; 95% confidence interval (95% CI): 1.32–2.00), lower for medical practitioners (OR: 0.36; 95% CI: 0.28–0.47) and did not differ for ‘other’ health care workers (OR: 1.07; 95% CI: 0. 87–1.32). The odds of infection in the second wave were higher in a health care setting (OR: 1.76; 95% CI: 1.28–2.41) than in the community. There were 120 outbreaks in health care settings with 1,428 cases, of which 56.7% (809/1,428) were health care workers. The majority (88/120; 73.8%) of outbreaks in health care settings occurred in the second wave of the epidemic, with 90.9% of these (80/88) occurring in Victoria. Conclusions In the second wave of the epidemic, when there was heightened community transmission, health care workers were more likely to be infected in the workplace. Throughout the epidemic, nurses were more likely to be infected than staff in other roles.

Background Large gatherings are associated with the spread of coronavirus 2019 disease (COVID-19); however, transmission dynamics are not well understood. We investigated a cluster of COVID-19 cases in returning Australian residents who attended wedding events in Bali, Indonesia, during 15– 21 March 2020. Attendees participated in various social events and were in close proximity, providing multiple opportunities for transmission. Methods We conducted a retrospective cohort study of the 41 attendees, of whom 17 participated in a structured interview that included history of illness, risk exposures and event attendance. We obtained data for the remaining 24 participants through corroborative histories and public health unit case investigations. Results COVID-19 was identified in 56% of attendees (23/41), with illness onset between 21 March and 2 April 2020. One secondary case was identified in a household contact of an attendee. The median age of cases was 31 years (range 3–64). One case was hospitalised and did not require critical care. There were no deaths. No cases occurred among six attendees who left prior to the actual wedding day. Guests attended multiple events and participated in high-risk transmission behaviours such as shaking hands, kissing, dancing, sharing drinks and sharing shisha (water pipes). Attack rates ranged from 64% to 87% for different exposures. We could not identify a single risk exposure that accounted for all cases; it is therefore likely there were multiple episodes of transmission. Conclusion Our investigation identified a high attack rate of COVID-19 among a cohort of wedding event attendees. Attendees engaged in close physical contact, shared drinks and shisha, and were in close proximity during the wedding events, which may have contributed to the high attack rate. This outbreak highlights the significant role social events can play in transmission of COVID-19 and underscores why it is important to limit gatherings and close physical contact to control the spread of the virus.