Background: Previous Australian study has shown an association between some influenza outbreaks and short-term mortality, but no such relationship with other respiratory viruses.

Objectives: To identify any relationship between respiratory viral outbreaks and short-term ED mortality in the two EDs in the Australian Capital Territory, population 440000.

Methods: Prospective descriptive study of ED presentations 12-Nov-2022 to 8-Dec-2023. Influenza and RSV outbreaks were defined by weekly positive test numbers >40 from the major provider, and COVID-19 by positive test numbers above 150% of the most recent weekly low, since reporting changes mid-study. Mortality was defined as death in hospital within 240 hours of most recent ED presentation.

Results: There were 160440 presentations by 104340 different patients across two hospitals, with 650 deaths within 10 days for mortality of 0.405% of presentations (95%CI 0.375-0.438). There was one long influenza outbreak of 21 weeks, starting 15-May-23, one RSV outbreak of 13 weeks starting 1-May-23, and three COVID-19 outbreaks, starting 21-Nov-22 for 9 weeks, 10-Apr-23 for 13 weeks and 16-Oct-23 for 7 weeks. Mortality was not related to any of these outbreaks: 0.41% (0.36-0.46) during Influenza compared to 0.40% (0.36-0.44) before and after. There was a higher ward admission rate during Influenza (22.5%, 22.1-22.8) than before and after (21.2%, 21.0-21.5) and during RSV  but no difference during COVID.

Conclusion: This study showed no association between respiratory infections and short-term mortality, despite a higher admission rate during the winter outbreaks. This is in contrast to international COVID-19 reports but similar to previous Australian experience.