Liu L, Li Y, Nielsen P V, Wei J, Jensen R L
Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.
Department of Civil Engineering, Aalborg University, Aalborg SV, Denmark.
Indoor Air. 2017 Mar;27(2):452-462. doi: 10.1111/ina.12314. Epub 2016 Jul 9.
The occurrence of close proximity infection for many respiratory diseases is often cited as evidence of large droplet and/or close contact transmission. We explored interpersonal exposure of exhaled droplets and droplet nuclei of two standing thermal manikins as affected by distance, humidity, ventilation, and breathing mode. Under the specific set of conditions studied, we found a substantial increase in airborne exposure to droplet nuclei exhaled by the source manikin when a susceptible manikin is within about 1.5 m of the source manikin, referred to as the proximity effect. The threshold distance of about 1.5 m distinguishes the two basic transmission processes of droplets and droplet nuclei, that is, short-range modes and the long-range airborne route. The short-range modes include both the conventional large droplet route and the newly defined short-range airborne transmission. We thus reveal that transmission occurring in close proximity to the source patient includes both droplet-borne (large droplet) and short-range airborne routes, in addition to the direct deposition of large droplets on other body surfaces. The mechanisms of the droplet-borne and short-range airborne routes are different; their effective control methods also differ. Neither the current droplet precautions nor dilution ventilation prevents short-range airborne transmission, so new control methods are needed.
许多呼吸道疾病发生的近距离感染常被引为大飞沫和/或密切接触传播的证据。我们研究了距离、湿度、通风和呼吸模式对两个站立式热人体模型呼出飞沫和飞沫核人际暴露的影响。在所研究的特定条件下，我们发现当易感人体模型在源人体模型约1.5米范围内时，源人体模型呼出的飞沫核在空气中的暴露显著增加，这被称为近距离效应。约1.5米的阈值距离区分了飞沫和飞沫核的两种基本传播过程，即短程模式和远程空气传播途径。短程模式包括传统的大飞沫途径和新定义的短程空气传播。因此，我们揭示了在源患者附近发生的传播除了大飞沫直接沉积在其他身体表面外，还包括飞沫传播（大飞沫）和短程空气传播途径。飞沫传播和短程空气传播途径的机制不同；它们的有效控制方法也不同。当前的飞沫预防措施和稀释通风都无法防止短程空气传播，因此需要新的控制方法。
