Environmental Health Department, Harvard T.H. Chan School of Public Health, Boston, MA 02115;
Environmental Health Department, Harvard T.H. Chan School of Public Health, Boston, MA 02115.
Proc Natl Acad Sci U S A. 2021 Feb 23;118(8). doi: 10.1073/pnas.2015482118.
Several lines of existing evidence support the possibility of airborne transmission of coronavirus disease 2019 (COVID-19). However, quantitative information on the relative importance of transmission pathways of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains limited. To evaluate the relative importance of multiple transmission routes for SARS-CoV-2, we developed a modeling framework and leveraged detailed information available from the cruise ship outbreak that occurred in early 2020. We modeled 21,600 scenarios to generate a matrix of solutions across a full range of assumptions for eight unknown or uncertain epidemic and mechanistic transmission factors. A total of 132 model iterations met acceptability criteria ( > 0.95 for modeled vs. reported cumulative daily cases and > 0 for daily cases). Analyzing only these successful model iterations quantifies the likely contributions of each defined mode of transmission. Mean estimates of the contributions of short-range, long-range, and fomite transmission modes to infected cases across the entire simulation period were 35%, 35%, and 30%, respectively. Mean estimates of the contributions of larger respiratory droplets and smaller respiratory aerosols were 41% and 59%, respectively. Our results demonstrate that aerosol inhalation was likely the dominant contributor to COVID-19 transmission among the passengers, even considering a conservative assumption of high ventilation rates and no air recirculation conditions for the cruise ship. Moreover, close-range and long-range transmission likely contributed similarly to disease progression aboard the ship, with fomite transmission playing a smaller role. The passenger quarantine also affected the importance of each mode, demonstrating the impacts of the interventions.
有几条现有证据表明，2019 年冠状病毒病（COVID-19）存在空气传播的可能性。然而，关于严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）传播途径相对重要性的定量信息仍然有限。为了评估 SARS-CoV-2 多种传播途径的相对重要性，我们开发了一个建模框架，并利用 2020 年初发生的游轮疫情的详细信息。我们模拟了 21600 种情况，生成了一个解决方案矩阵，涵盖了 8 个未知或不确定的流行病和机械传播因素的全范围假设。共有 132 次模型迭代符合可接受性标准（模型预测的累计日病例与报告的日病例之比>0.95，日病例之比>0）。仅分析这些成功的模型迭代，可以量化每种定义的传播模式的可能贡献。在整个模拟期间，短程、远程和媒介传播模式对感染病例的平均估计贡献分别为 35%、35%和 30%。较大的呼吸道飞沫和较小的呼吸道气溶胶的平均估计贡献分别为 41%和 59%。我们的研究结果表明，即使考虑到游轮高通风率和无空气再循环条件的保守假设，气溶胶吸入也可能是 COVID-19 传播的主要因素。此外，近距离和远程传播可能对船上疾病的进展同样重要，而媒介传播的作用较小。乘客检疫也影响了每种模式的重要性，展示了干预措施的影响。
