Simulating Transmission Scenarios of the Delta Variant of SARS-CoV-2 in Australia

Abstract

An outbreak of the Delta (B.1.617.2) variant of SARS-CoV-2 that began around mid-June 2021 in Sydney, Australia, quickly developed into a nation-wide epidemic. The ongoing epidemic is of major concern as the Delta variant is more infectious than previous variants that circulated in Australia in 2020. Using a re-calibrated agent-based model, we explored a feasible range of non-pharmaceutical interventions, including case isolation, home quarantine, school closures, and stay-at-home restrictions (i.e., “social distancing.”) Our modelling indicated that the levels of reduced interactions in workplaces and across communities attained in Sydney and other parts of the nation were inadequate for controlling the outbreak. A counter-factual analysis suggested that if 70% of the population followed tight stay-at-home restrictions, then at least 45 days would have been needed for new daily cases to fall from their peak to below ten per day. Our model predicted that, under a progressive vaccination rollout, if 40–50% of the Australian population follow stay-at-home restrictions, the incidence will peak by mid-October 2021: the peak in incidence across the nation was indeed observed in mid-October. We also quantified an expected burden on the healthcare system and potential fatalities across Australia.

Modelling herd immunity requirements in Queensland: impact of vaccination effectiveness, hesitancy and variants of SARS-CoV-2

“…Ideally, this unvaccinated subset would only consist of members of the population who are unable to receive the vaccine due to medical or health-related reasons. In practice, idealized herd immunity for SARS-CoV-2 is likely to be difficult to reach, as supported by various models [7][8][9][10][11][12][13][14][15][16][17][18][19]. Thus, it is important to determine whether there is a 'practical' vaccination coverage level at which introduced infections do not lead to outbreaks, or small outbreaks can be effectively suppressed with only mild additional public health interventions such as testing, contact tracing, isolation and quarantine (TTIQ).…”

The effects of local homogeneity assumptions in metapopulation models of infectious disease

“…These discrepancies were reported to increase with higher values of the basic reproductive number R 0 [15], and hence, this tendency forms an elevated concern in modelling more infectious diseases, such as the COVID-19. Indeed, pandemic spread of SARS-CoV-2, and its more infectious Delta (B.1.617.2) variant, was often driven by structural factors, especially in areas characterised by socioeconomic disadvantage profiles, with high-density housing, multi-generational and shared households, higher concentrations of essential workers [20],…”

Do COVID-19 CT features vary between patients from within and outside mainland China? Findings from a meta-analysis

“…Given the fact that the transmission ability of COVID-19 is stronger and the incidence of mortality is relatively higher (6,7), rapid and accurate diagnostic methods show their great significance for the prevention, control, and management of COVID-19. Real-time fluorescence polymerase chain reaction (RT-PCR) remains the current gold standard for COVID-19 diagnosis (8); however, this diagnosis method has some shortcomings: (1) it is very time-consuming to obtain the results after sampling and may lead to experimental errors caused by manual handling (9, 10), (2) there are a high rate of falsenegative results (11), where there were even repeated negatives confirmed by other methods for patients when viral load is insufficient (12), (3) not all hospitals and clinics can implement these methods or the supply and quality of the reagents cannot keep up with the demand in time (13,14), (4) the severity, progression, and the evaluation of patients cannot be judged or traced (11,15,16).…”