Institute for Health and the Built Environment, University of Oregon, Portland, Oregon, USA.
Energy Studies in Buildings Laboratory, University of Oregon, Eugene, Oregon, USA.
Clin Infect Dis. 2022 Aug 24;75(1):e174-e184. doi: 10.1093/cid/ciac006.
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.
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.
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.
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.
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，针对人类活动、建筑参数和环境缓解策略，对严重急性呼吸综合征冠状病毒 2 病毒载量进行环境特征描述对于控制疾病传播至关重要。
我们招募了 11 名经诊断患有 COVID-19 的参与者，让他们分别在一个受控室内，在一系列环境条件下进行特定的体育活动；我们在每位参与者的 3 天时间内采集人体和环境样本。
在此我们表明，鼻腔样本中病毒载量的增加（以较低的 RNA 循环阈值（CT）值表示）与近场（1.2 m）和远场（3.5 m）中捕获的环境气溶胶和表面上更高的病毒载量相关。我们还发现，远场气溶胶中的病毒载量与 1-2.5 µm 范围内的粒子数量呈正相关。此外，我们发现增加通风和过滤显著降低了气溶胶和表面的病毒载量，而较高的相对湿度导致气溶胶病毒载量降低，表面病毒载量升高，这与相对湿度较高时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）的呼吸颗粒能更好地描述近场气溶胶病毒载量的变化。
我们的研究结果表明，建筑运行实践，如通风、过滤和加湿，可大大降低环境气溶胶病毒载量，从而降低吸入剂量，应优先考虑这些措施以改善建筑健康和安全。
