The SIR (‘susceptible-infectious-recovered’) formulation is used to uncover the generic spread mechanisms observed by COVID-19 dynamics globally, especially in the early phases of infectious spread. During this early period, potential controls were not effectively put in place or enforced in many countries. Hence, the early phases of COVID-19 spread in countries where controls were weak offer a unique perspective on the ensemble-behavior of COVID-19 basic reproduction number R_o inferred from SIR formulation. The work here shows that there is global convergence (i.e., across many nations) to an uncontrolled R_o = 4.5 that describes the early time spread of COVID-19. This value is in agreement with independent estimates from other sources reviewed here and adds to the growing consensus that the early estimate of R_o = 2.2 adopted by the World Health Organization is low. A reconciliation between power-law and exponential growth predictions is also featured within the confines of the SIR formulation. The effects of testing ramp-up and the role of ‘super-spreaders’ on the inference of R_o are analyzed using idealized scenarios. Implications for evaluating potential control strategies from this uncontrolled R_o are briefly discussed in the context of the maximum possible infected fraction of the population (needed to assess health care capacity) and mortality (especially in the USA given diverging projections). Model results indicate that if intervention measures still result in R_o > 2.7 within 44 days after first infection, intervention is unlikely to be effective in general for COVID-19.

SIR（“易感-感染-恢复”）公式用于揭示全球范围内观察到的 COVID-19 动态的一般传播机制，特别是在感染传播的早期阶段。在此早期阶段，许多国家并未有效落实或执行潜在的控制措施。因此，COVID-19 在控制薄弱的国家传播的早期阶段为从 SIR 公式推断出的COVID-19 基本再生数R _o的整体行为提供了独特的视角。这里的工作表明，全球趋同（即跨许多国家）达到不受控制的Ro ₌ 4.5，这描述了 COVID-19 的早期传播。该值与此处审查的其他来源的独立估计值一致，并增加了越来越多的共识，即世界卫生组织采用的Ro _{= 2.2 的早期估计值较低。}SIR 公式的范围内还具有幂律和指数增长预测之间的协调。使用理想化场景分析了测试提升的影响以及“超级传播者”对R _{o推论的作用。}在最大可能的人口感染比例（需要评估医疗保健能力）和死亡率（特别是在美国，考虑到不同的预测）的背景下，简要讨论了评估这种不受控制的R o 的潜在控制策略的含义_。模型结果表明，如果干预措施在首次感染后 44 天内仍导致Ro > 2.7，_{则干预措施总体上不太可能对 COVID-19 有效。}