Rocky Mountain Center for Occupational and Environmental Health, University of Utah, Salt Lake City, Utah.
Department of Family and Preventive Medicine, School of Medicine, University of Utah, Salt Lake City, Utah.
J Occup Environ Hyg. 2021 Jul;18(7):345-360. doi: 10.1080/15459624.2021.1926468. Epub 2021 Jun 15.
First responders may have high SARS-CoV-2 infection risks due to working with potentially infected patients in enclosed spaces. The study objective was to estimate infection risks per transport for first responders and quantify how first responder use of N95 respirators and patient use of cloth masks can reduce these risks. A model was developed for two Scenarios: an ambulance transport with a patient actively emitting a virus in small aerosols that could lead to airborne transmission (Scenario 1) and a subsequent transport with the same respirator or mask use conditions, an uninfected patient; and remaining airborne SARS-CoV-2 and contaminated surfaces due to aerosol deposition from the previous transport (Scenario 2). A compartmental Monte Carlo simulation model was used to estimate the dispersion and deposition of SARS-CoV-2 and subsequent infection risks for first responders, accounting for variability and uncertainty in input parameters (i.e., transport duration, transfer efficiencies, SARS-CoV-2 emission rates from infected patients, etc.). Infection risk distributions and changes in concentration on hands and surfaces over time were estimated across sub-Scenarios of first responder respirator use and patient cloth mask use. For Scenario 1, predicted mean infection risks were reduced by 69%, 48%, and 85% from a baseline risk (no respirators or face masks used) of 2.9 × 10 ± 3.4 × 10 when simulated first responders wore respirators, the patient wore a cloth mask, and when first responders and the patient wore respirators or a cloth mask, respectively. For Scenario 2, infection risk reductions for these same Scenarios were 69%, 50%, and 85%, respectively (baseline risk of 7.2 × 10 ± 1.0 × 10). While aerosol transmission routes contributed more to viral dose in Scenario 1, our simulations demonstrate the ability of face masks worn by patients to additionally reduce surface transmission by reducing viral deposition on surfaces. Based on these simulations, we recommend the patient wear a face mask and first responders wear respirators, when possible, and disinfection should prioritize high use equipment.
急救人员在封闭空间中与可能感染的患者一起工作，可能面临较高的 SARS-CoV-2 感染风险。本研究旨在评估急救人员每次转运的感染风险，并量化急救人员使用 N95 口罩和患者使用布制口罩如何降低这些风险。研究建立了两种情景的模型：一种是在气溶胶中病毒活跃排放可能导致空气传播的情况下（情景 1），使用救护车转运患者；另一种是在相同的口罩使用条件下（情景 2），使用相同的口罩，转运无症状患者。情景 1 中，患者在气溶胶中排放病毒，导致前一次转运后遗留的空气传播 SARS-CoV-2 和污染表面；情景 2 中，空气中和表面的 SARS-CoV-2 来自之前转运过程中气溶胶的沉积。使用隔室蒙特卡罗模拟模型来估计 SARS-CoV-2 的分散和沉积，以及随后急救人员的感染风险，同时考虑输入参数的变异性和不确定性（例如，转运时间、转移效率、感染患者的 SARS-CoV-2 排放率等）。根据急救人员使用口罩和患者使用布制口罩的不同子情景，估计了感染风险分布和手部和表面上 SARS-CoV-2 浓度随时间的变化。在情景 1 中，与不使用口罩或面罩的基线风险（2.9×10 ± 3.4×10）相比，模拟急救人员佩戴口罩、患者佩戴布制口罩以及急救人员和患者分别佩戴口罩或布制口罩时，预测的平均感染风险分别降低了 69%、48%和 85%。在情景 2 中，这些情景的感染风险降低分别为 69%、50%和 85%（基线风险为 7.2×10 ± 1.0×10）。虽然气溶胶传播途径在情景 1 中对病毒剂量的贡献更大，但我们的模拟表明，患者佩戴口罩除了通过减少病毒在表面上的沉积来降低表面传播外，还能降低感染风险。基于这些模拟，我们建议在可能的情况下，患者佩戴口罩，急救人员佩戴口罩，并应优先对高使用设备进行消毒。
