The 2020 Olympic/Paralympic Games have been postponed to 2021, due to the COVID-19 pandemic. We developed a model that integrated source–environment–receptor pathways to evaluate how preventive efforts can reduce the infection risk among spectators at the opening ceremony of Tokyo Olympic Games. We simulated viral loads of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emitted from infectors through talking/coughing/sneezing and modeled temporal environmental behaviors, including virus inactivation and transfer. We performed Monte Carlo simulations to estimate the expected number of newly infected individuals with and without preventive measures, yielding the crude probability of a spectator being an infector among the 60,000 people expected to attend the opening ceremony. Two indicators, i.e., the expected number of newly infected individuals and the newly infected individuals per infector entry, were proposed to demonstrate the extent of achievable infection risk reduction levels by implementing possible preventive measures. A no-prevention scenario produced 1.5–1.7 newly infected individuals per infector entry, whereas a combination of cooperative preventive measures by organizers and the spectators achieved a 99% risk reduction, corresponding to 0.009–0.012 newly infected individuals per infector entry. The expected number of newly infected individuals was calculated as 0.005 for the combination of cooperative preventive scenarios with the crude probability of a spectator being an infector of 1 × 10⁻⁵. Based on our estimates, a combination of cooperative preventions between organizers and spectators is required to prevent a viral spread at the Tokyo Olympic/Paralympic Games. Further, under the assumption that society accepts < 10 newly infected persons traced to events held during the entire Olympic/Paralympic Games, we propose a crude probability of infectors of < 5 × 10⁻⁵ as a benchmark for the suppression of the infection. This is the first study to develop a model that can assess the infection risk among spectators due to exposure pathways at a mass gathering event.

由于 COVID-19 大流行，2020 年奥运会/残奥会已推迟到 2021 年。我们开发了一个整合源-环境-受体通路的模型，以评估预防措施如何降低东京奥运会开幕式观众感染风险。我们模拟了感染者通过说话/咳嗽/打喷嚏释放的严重急性呼吸系统综合症冠状病毒 2 (SARS-CoV-2) 的病毒载量，并模拟了时间环境行为，包括病毒灭活和转移。我们进行了蒙特卡罗模拟，以估计在采取和不采取预防措施的情况下新感染者的预期数量，从而得出在预计参加开幕式的 60,000 人中，观众是感染者的粗略概率。两个指标，即 提出了新感染者的预期数量和每次感染者进入的新感染者人数，以证明通过实施可能的预防措施可实现的感染风险降低程度。无预防方案每次感染者进入会产生 1.5-1.7 个新感染者，而组织者和观众的合作预防措施相结合实现了 99% 的风险降低，对应于每个感染者进入 0.009-0.012 个新感染者。对于合作预防方案与旁观者是感染者的粗概率为 1 × 10 的组合，新感染个体的预期数量计算为 0.005 建议通过实施可能的预防措施来证明可实现的感染风险降低程度。无预防方案每次感染者进入会产生 1.5-1.7 个新感染者，而组织者和观众的合作预防措施相结合实现了 99% 的风险降低，对应于每个感染者进入 0.009-0.012 个新感染者。对于合作预防方案与旁观者是感染者的粗概率为 1 × 10 的组合，新感染个体的预期数量计算为 0.005 建议通过实施可能的预防措施来证明可实现的感染风险降低程度。无预防方案每次感染者进入会产生 1.5-1.7 个新感染者，而组织者和观众的合作预防措施相结合实现了 99% 的风险降低，对应于每个感染者进入 0.009-0.012 个新感染者。对于合作预防方案与旁观者是感染者的粗概率为 1 × 10 的组合，新感染个体的预期数量计算为 0.005 而组织者和观众的合作预防措施相结合实现了 99% 的风险降低，相当于每次感染者进入 0.009-0.012 新感染者。对于合作预防方案与旁观者是感染者的粗概率为 1 × 10 的组合，新感染个体的预期数量计算为 0.005 而组织者和观众的合作预防措施相结合实现了 99% 的风险降低，相当于每次感染者进入 0.009-0.012 新感染者。对于合作预防方案与旁观者是感染者的粗概率为 1 × 10 的组合，新感染个体的预期数量计算为 0.005^－5．根据我们的估计，需要组织者和观众之间的合作预防相结合，以防止东京奥运会/残奥会的病毒传播。此外，假设社会接受< 10 名追踪到整个奥运会/残奥会期间举办的事件的新感染者，我们提出了< 5 × 10 ^-5感染者的粗概率作为抑制感染的基准。这是第一项开发模型的研究，该模型可以评估由于群众集会活动中的暴露途径而导致的观众感染风险。