Abstract

Environmental air sampling of the SARS-CoV-2 virus in occupational and community settings is pertinent to reduce and monitor the spread of the COVID pandemic. However, there is a general lack of standardized procedures for airborne virus sampling and limited knowledge of how sampling and storage stress impact the recovery of captured airborne viruses. Since filtration is one of the commonly used methods to capture airborne viruses, this study analyzed the effect of sampling and storage stress on SARS-CoV-2 surrogate virus (human coronavirus OC43, or HCoV-OC43) captured by filters. HCoV-OC43, a simulant of the SARS-CoV-2, was aerosolized and captured by PTFE-laminated filters. The impact of sampling stress was evaluated by comparing the RNA yields recovered when sampled at 3 L/min and 10 L/min and for 10 min and 60 min; in one set of experiments, additional stress was added by passing clean air through filters with the virus for 1, 5, and 15 hr. The impact of storage stress was designed to examine RNA recovery from filters at room temperature (25 °C) and refrigerated conditions (4 °C) for up to 1 week of storage. To our knowledge, this is the first report on using HCoV-OC43 aerosol in air sampling experiments, and the mode diameter of the virus aerosolized from the growth medium was 40–60 nm as determined by SMPS + CPC system (TSI Inc.) and MiniWRAS (Grimm Inc.) measurements. No significant difference was found in virus recovery between the two sampling flow rates and different sampling times (p > 0.05). However, storage at room temperature (25 °C) yielded ∼2x less RNA than immediate processing and storage at refrigerated conditions (4 °C). Therefore, it is recommended to store filter samples with viruses at 4 °C up to 1 week if the immediate analysis is not feasible. Although the laminated PTFE filter used in this work purposefully does not include a non-PTFE backing, the general recommendations for handling and storing filter samples with viral particles are likely to apply to other filter types.

摘要

在职业和社区环境中对 SARS-CoV-2 病毒进行环境空气采样有助于减少和监测 COVID 大流行的传播。然而，普遍缺乏空气传播病毒采样的标准化程序，并且对采样和储存压力如何影响捕获的空气传播病毒的回收率的了解有限。由于过滤是捕获空气传播病毒的常用方法之一，本研究分析了采样和储存压力对过滤器捕获的 SARS-CoV-2 替代病毒（人冠状病毒 OC43，或 HCoV-OC43）的影响。HCoV-OC43 是 SARS-CoV-2 的模拟物，被 PTFE 层压过滤器雾化和捕获。通过比较以 3 L/min 和 10 L/min 以及 10 min 和 60 min 采样时回收的 RNA 产量来评估采样压力的影响；在一组实验中，通过使清洁空气通过带有病毒的过滤器 1、5 和 15 小时，增加了额外的压力。储存压力的影响旨在检查在室温 (25°C) 和冷藏条件 (4°C) 下储存长达 1 周的过滤器中的 RNA 回收率。据我们所知，这是在空气采样实验中使用 HCoV-OC43 气溶胶的第一份报告，通过 SMPS + CPC 系统（TSI Inc.）和MiniWRAS (Grimm Inc.) 测量。两种采样流速和不同采样时间的病毒回收率无显着差异（p > 0.05）。然而，在室温 (25°C) 下储存产生的 RNA 比在冷藏条件 (4°C) 下立即加工和储存少 2 倍。所以，如果立即分析不可行，建议将带有病毒的过滤样品在 4 °C 下保存 1 周。尽管在这项工作中使用的层压 PTFE 过滤器故意不包括非 PTFE 背衬，但处理和储存带有病毒颗粒的过滤器样品的一般建议可能适用于其他过滤器类型。