Modelling the impact of COVID-19 in Australia to inform transmission reducing measures and health system preparedness

Robert Moss; James Wood; Damien Brown; Freya Shearer; Andrew J Black; Allen Cheng; James M McCaw; Jodie McVernon

The model of patient flows for mild and severe disease is represented conceptually in Figure 1 . At baseline, we assume that half of available consulting and admission capacity across all sectors and services is available to COVID-19 patients. Mild cases present to primary care until capacity is exceeded. Severe cases access the hospital system through ED and from there are triaged to a ward or ICU bed according to need, if available. Requirements for critical care are assumed to increase steeply with age with the consequence that about 60% of all infections requiring ICU admission occur in individuals aged 70 years and over ( Table 2) . As ward beds reach capacity, the ability of emergency departments to triage patients is reduced because of bed block, meaning that not all patients who need care are medically assessed, although some will still be able to access primary care. The model allows for repeat representations within and between primary care and hospital services, and progression from ward to intensive care, with length of stay as shown ( Table 2 ). Model structure and assumptions are based on publicly available data on the Australian health care system, and expert elicitation. Full model details are provided in Supplementary material.