Supply shortages of N95 respirators during the coronavirus disease 2019 (COVID-19) pandemic have motivated institutions to develop feasible and effective N95 respirator reuse strategies. In particular, heat decontamination is a treatment method that scales well and can be implemented in settings with variable or limited resources. Prior studies using multiple inactivation methods, however, have often focused on a single virus under narrowly defined conditions, making it difficult to develop guiding principles for inactivating emerging or difficult-to-culture viruses. We systematically explored how temperature, humidity, and virus deposition solutions impact the inactivation of viruses deposited and dried on N95 respirator coupons. We exposed four virus surrogates across a range of structures and phylogenies, including two bacteriophages (MS2 and phi6), a mouse coronavirus (murine hepatitis virus [MHV]), and a recombinant human influenza A virus subtype H3N2 (IAV), to heat treatment for 30 min in multiple deposition solutions across several temperatures and relative humidities (RHs). We observed that elevated RH was essential for effective heat inactivation of all four viruses tested. For heat treatments between 72°C and 82°C, RHs greater than 50% resulted in a >6-log₁₀ inactivation of bacteriophages, and RHs greater than 25% resulted in a >3.5-log₁₀ inactivation of MHV and IAV. Furthermore, deposition of viruses in host cell culture media greatly enhanced virus inactivation by heat and humidity compared to other deposition solutions, such as phosphate-buffered saline, phosphate-buffered saline with bovine serum albumin, and human saliva. Past and future heat treatment methods must therefore explicitly account for deposition solutions as a factor that will strongly influence observed virus inactivation rates. Overall, our data set can inform the design and validation of effective heat-based decontamination strategies for N95 respirators and other porous surfaces, especially for emerging viruses that may be of immediate and future public health concern.

中文翻译：

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湿度和沉积溶液在 N95 口罩热处理灭活病毒中起关键作用

2019 年冠状病毒病 (COVID-19) 大流行期间 N95 呼吸器供应短缺，促使机构制定可行且有效的 N95 呼吸器重复使用策略。特别是，热净化是一种规模化良好的处理方法，可以在资源可变或有限的环境中实施。然而，先前使用多种灭活方法的研究通常集中在狭义条件下的单一病毒上，因此很难制定灭活新出现或难以培养的病毒的指导原则。我们系统地探索了温度、湿度和病毒沉积溶液如何影响 N95 呼吸器试样上沉积和干燥的病毒的灭活。我们在一系列结构和系统发育中暴露了四种病毒替代物，包括两种噬菌体（MS2 和 phi6）、一种小鼠冠状病毒（鼠肝炎病毒 [MHV]）和一种重组人甲型流感病毒亚型 H3N2（IAV），在多种温度和相对湿度的多种沉积溶液中热处理 30 分钟(RH)。我们观察到升高的 RH 对于所有四种测试病毒的有效热灭活至关重要。对于 72°C 和 82°C 之间的热处理，大于 50% 的 RH 导致 >6-log₁₀噬菌体失活，RH 大于 25% 导致MHV 和 IAV 失活>3.5-log ₁₀。此外，与其他沉积溶液（如磷酸盐缓冲盐水、含牛血清白蛋白的磷酸盐缓冲盐水和人唾液）相比，病毒在宿主细胞培养基中的沉积大大增强了热和湿度对病毒的灭活作用。因此，过去和未来的热处理方法必须明确地将沉积溶液作为一个会强烈影响观察到的病毒灭活率的因素。总体而言，我们的数据集可以为 N95 呼吸器和其他多孔表面的有效热基净化策略的设计和验证提供信息，尤其是对于可能引起当前和未来公共卫生问题的新兴病毒。