Background Several studies indicate that coronavirus disease 2019 (COVID-19) is primarily transmitted within indoor spaces. Therefore, environmental characterization of severe acute respiratory syndrome coronavirus 2 viral load with respect to human activity, building parameters, and environmental mitigation strategies is critical to combat disease transmission. Methods We recruited 11 participants diagnosed with COVID-19 to individually occupy a controlled chamber and conduct specified physical activities under a range of environmental conditions; we collected human and environmental samples over a period of 3 days for each participant. Results Here we show that increased viral load, measured by lower RNA cycle threshold (CT) values, in nasal samples is associated with higher viral loads in environmental aerosols and on surfaces captured in both the near field (1.2 m) and far field (3.5 m). We also found that aerosol viral load in far field is correlated with the number of particles within the range of 1–2.5 µm. Furthermore, we found that increased ventilation and filtration significantly reduced aerosol and surface viral loads, while higher relative humidity resulted in lower aerosol and higher surface viral load, consistent with an increased rate of particle deposition at higher relative humidity. Data from near field aerosol trials with high expiratory activities suggest that respiratory particles of smaller sizes (0.3–1 µm) best characterize the variance of near field aerosol viral load. Conclusions Our findings indicate that building operation practices such as ventilation, filtration, and humidification substantially reduce the environmental aerosol viral load and therefore inhalation dose, and should be prioritized to improve building health and safety.

中文翻译：

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量化控制室中气溶胶病毒载量的环境缓解情况，参与者被诊断患有 2019 年冠状病毒病

背景 多项研究表明，2019 年冠状病毒病 (COVID-19) 主要在室内空间传播。因此，关于人类活动、建筑参数和环境缓解策略的严重急性呼吸综合征冠状病毒 2 病毒载量的环境特征对于对抗疾病传播至关重要。方法 我们招募了 11 名被诊断为 COVID-19 的参与者，他们分别占据一个受控室并在一系列环境条件下进行指定的体育活动；我们在 3 天内为每位参与者收集了人类和环境样本。结果 在这里，我们显示通过较低的 RNA 循环阈值 (CT) 值测量的病毒载量增加，鼻样本中的病毒载量与环境气溶胶和近场（1.2 m）和远场（3.5 m）捕获的表面上的较高病毒载量有关。我们还发现，远场气溶胶病毒载量与 1-2.5 µm 范围内的颗粒数量相关。此外，我们发现增加通风和过滤可显着降低气溶胶和表面病毒载量，而较高的相对湿度导致较低的气溶胶和较高的表面病毒载量，这与较高相对湿度下颗粒沉积率增加一致。来自具有高呼气活动的近场气溶胶试验的数据表明，较小尺寸（0.3-1 µm）的呼吸颗粒最能表征近场气溶胶病毒载量的变化。