短期事件中传染病空气传播规律及时均暴露剂量不确定性研究

Viruses of many respiratory infectious diseases can attach to human expiratory droplet nuclei and transmit quickly between persons via air. Understanding the transmission characteristics and mechanisms is therefore of fundamental significance for formulating high-efficient control measures and in turn reducing largely the number of deaths and illness leaves as well as huge economic loss. Past studies on airborne transmission are limited to steady-state circumstances (namely with steady-state indoor background concentration). Recently the applicant investigated experimentally airborne transmission during short-term events (namely, with building-up indoor background concentration, e.g., physician consultations and short meetings) and obtained some results that against the classic risk-distance relation established in the past studies under steady-state conditions, which, however, cannot reveal the transmission characteristics and explain the transmission mechanisms. This project intends to systematically investigate airborne transmission during short-term events. Particular attentions are paid to revealing first the building-up characteristics of direct and indirect transmission and second the random uncertainty of time-averaged exposure with the influence of various environmental and personal factors. Based on high-frequency climate chamber measurements, improvements on CFD model will be made to establish an unsteady CFD simulation method that is suitable for the investigated problem. A new separating-coupling analysis method for direct and indirect exposure will be developed and the unsteady exposure characteristics and mechanisms of airborne transmission during short-term events revealed. This project will also analyze the statistical correlations of the time-averaged exposure with event duration and event conditions and develop new model and method for evaluating the risk of cross infection during short-term events. The findings of this study would improve our understanding of airborne transmission and provide useful information for formulating accurate and energy-saving control measures for short-term events.

许多呼吸道传染病病毒可附着于人呼出飞沫核通过空气在人际间快速传播，理清其传播规律和机理对制定高效控制措施从而大幅减少死亡率、病假率和巨额经济损失有重要意义。目前呼吸道传染病空气传播研究仅限于稳态情形（室内背景浓度已处于稳态）；申请人对非稳态短期暴露事件（室内背景浓度尚处于积累上升阶段，如医院门诊咨询和短期会议）进行了初步实验研究，发现时均暴露剂量可能存在与距离和时长的反常识依存关系，但尚不能揭示其暴露规律和机理。本项目拟系统研究短期事件中直接和间接暴露的时序特征以及在环境和人员因素作用下的时均暴露剂量随机不确定性等关键科学问题，结合环境舱实验改进CFD模型，建立针对短期事件的非稳态数值模拟方法，发展直接和间接暴露分离耦合分析方法，揭示短期事件非稳态暴露规律和机理，研究时均暴露剂量对时长和事件的统计相关性，发展短期事件感染概率评估模型和方法，为制定针对短期事件的高效节能控制措施提供理论依据。

气溶胶传播是呼吸道传染病的主要传播途径之一，也是最难实施高效精准防控的传播途径。厘清气溶胶传播机理，有助于增强对呼吸道传染病在密闭空间传播规律的认识，是制定有针对性防控措施的基本前提。然而，关于气溶胶传播的现有研究、应对指南、防控措施等几乎都局限于稳态情形（即假设暴露事件已持续较长时间），鲜有针对现实生活中广泛存在的短期暴露事件（如医院门诊咨询、食堂就餐、短期会议）。.本项目首先优化改进了现场测试、环境舱实验和数值模拟相关研究方法，使其更适用于本项目研究问题，进而系统地研究了短期暴露事件中人际间传播规律，特别是在不同环境和人员因素作用下解耦了直接暴露和间接暴露的时序特征，揭示了短期事件中时均暴露剂量随机不确定性规律，并研究了针对典型短期暴露事件的精准防控方法。.本项目提出了利用示踪气体和颗粒物模拟人体呼出物的适用范围和限制，制备了简易发热假人，提出了吸入暴露的准确评估和测量方法，建立了针对短期事件的非稳态CFD模拟方法；通过解耦直接暴露和间接暴露，发现了直接暴露在短期事件中的主导作用，建立了短期暴露瞬态暴露量的动态分析方法；揭示了短期暴露事件中人员呼出飞沫核的近距离迁移规律和非稳态短期时均暴露规律，发现了由于两人之间物理隔离措施的存在而导致的一种新的传播路径；揭示了医护人员和患者之间的短期暴露规律以及不同时间进入诊室的患者之间的短期暴露和交叉传播特征；揭示了个人防护设备面罩对人员吸入暴露的影响及动态特性；提出了间歇性人员在室率的全空间交叉感染风险控制方法；分析了现有防控措施在考虑短期暴露事件方面存在的不足并提出改进建议。.本项目建立了对短期暴露事件传播规律和暴露风险不确定性的认识，完善和拓展了呼吸道传染病气溶胶传播理论，有利于解答现有传播过程中存在的部分疑虑，为制定针对短期暴露事件的精准防控措施提供了科学依据，推动了低碳、高效、科学建筑防疫向前迈进一步。