As of July 2021, there is a continuing outbreak of the B.1.617.2 (Delta) variant of SARS-CoV-2 in Sydney, Australia. The outbreak is of major concern as the Delta variant is estimated to have twice the reproductive number to previous variants that circulated in Australia in 2020, which is worsened by low levels of acquired immunity in the population. Using a re-calibrated agent-based model, we explored a feasible range of non-pharmaceutical interventions, in terms of both mitigation (case isolation, home quarantine) and suppression (school closures, social distancing). Our nowcasting modelling indicated that the level of social distancing currently attained in Sydney is inadequate for the outbreak control. A counter-factual analysis suggested that if 80% of agents comply with social distancing, then at least a month is needed for the new daily cases to reduce from their peak to below ten. A small reduction in social distancing compliance to 70% lengthens this period to over two months.

中文翻译：

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澳大利亚 SARS-CoV-2 Delta 变体的临近传播和抑制

截至 2021 年 7 月，SARS-CoV-2 的 B.1.617.2 (Delta) 变体在澳大利亚悉尼持续爆发。此次爆发是一个重大问题，因为估计 Delta 变体的繁殖数量是 2020 年在澳大利亚传播的先前变体的两倍，而人口中获得的免疫力水平低则进一步恶化。使用重新校准的基于代理的模型，我们探索了一系列可行的非药物干预措施，包括缓解（病例隔离、家庭隔离）和抑制（学校停课、社会疏远）。我们的临近预报模型表明，悉尼目前达到的社交距离水平不足以控制疫情。一项反事实分析表明，如果 80% 的代理人遵守社交距离，那么至少需要一个月的时间，新的每日病例才能从高峰减少到十个以下。社会疏远遵守率小幅减少至 70% 会将这段时间延长至两个多月。