During the 2020 COVID‐19 pandemic, an outbreak occurred following attendance of a symptomatic index case at a weekly rehearsal on 10 March of the Skagit Valley Chorale (SVC). After that rehearsal, 53 members of the SVC among 61 in attendance were confirmed or strongly suspected to have contracted COVID‐19 and two died. Transmission by the aerosol route is likely; it appears unlikely that either fomite or ballistic droplet transmission could explain a substantial fraction of the cases. It is vital to identify features of cases such as this to better understand the factors that promote superspreading events. Based on a conditional assumption that transmission during this outbreak was dominated by inhalation of respiratory aerosol generated by one index case, we use the available evidence to infer the emission rate of aerosol infectious quanta. We explore how the risk of infection would vary with several influential factors: ventilation rate, duration of event, and deposition onto surfaces. The results indicate a best‐estimate emission rate of 970 ± 390 quanta/h. Infection risk would be reduced by a factor of two by increasing the aerosol loss rate to 5 h⁻¹ and shortening the event duration from 2.5 to 1 h.

中文翻译：

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在 Skagit Valley Chorale 超级传播事件中通过吸入呼吸道气溶胶传播 SARS-CoV-2

在 2020 年 COVID-19 大流行期间，在 3 月 10 日斯卡吉特山谷合唱团 (SVC) 的每周排练中出现了有症状的指示病例后爆发了疫情。在那次排练之后，出席的 61 名 SVC 成员中有 53 名被确认或强烈怀疑感染了 COVID-19，其中两人死亡。很可能通过气溶胶途径传播；看来，无论是污染物还是弹道飞沫传播都不太可能解释很大一部分病例。识别此类案例的特征以更好地了解促进超级传播事件的因素至关重要。基于一个有条件的假设，即这次暴发期间的传播主要是吸入一个指示病例产生的呼吸道气溶胶，我们使用现有证据来推断气溶胶传染性量子的排放率。我们探讨了感染风险如何随几个影响因素而变化：通风率、事件持续时间和表面沉积。结果表明最佳估计排放速率为 970 ± 390 量子/小时。通过将气溶胶损失率提高到 5 小时，感染风险将降低两倍^-1并将事件持续时间从 2.5 缩短到 1 小时。