Department of Cardiac, Thoracic, Vascular Sciences and Public Health, Unit of Hygiene and Public Health, University of Padua, Padua, Italy.
Sci Total Environ. 2021 Mar 15;760:143329. doi: 10.1016/j.scitotenv.2020.143329. Epub 2020 Nov 2.
Clinical detection of SARS-CoV-2 RNA in stools supports the idea of wastewater-based epidemiology (WBE) as a precious tool for COVID-19 environmental surveillance. Successful detection of SARS-CoV-2 RNA in untreated wastewaters has been reported in several countries. This study investigated the presence and persistence of viral RNA in treated and untreated wastewaters in Padua, Italy. An urban experimental network of sampling sites was tested for prospective surveillance activities.
Seven sampling sites (i.e. wastewater pumping stations, plant inlets and outlets) were selected from the two main municipal wastewater treatment plant systems. Eleven grab samples (9 untreated, 2 treated wastewaters) were collected on 2 dates. All samples were tested at t0 for SARS-CoV-2 RNA and t1 = 24 h to investigate its persistence, at room temperature and under refrigerated conditions. Overall, 33 sub-samples were concentrated by ultrafiltration and tested for molecular detection of viral RNA with two RT-qPCR assays.
At t0, positivity for at least one RT-qPCR assay was achieved by 4/9 untreated wastewater samples and 2/2 tertiary treated samples. A minimum SARS-CoV-2 titer of 4.8-4.9 log10 gc/L was estimated. At t1, three refrigerated subsamples were positive as well. The two RT-qPCR assays showed differential sensitivity, with the N assay detecting 90% of successful amplifications.
SARS-CoV-2 RNA was detected in untreated and treated wastewaters. Its persistence after 24 h was demonstrated in subsamples kept at 4 °C. Hospitalization data suggested an approximate WBE detection power of 1 COVID-19 case per 531 inhabitants. The possible role of WBE in COVID-19 environmental surveillance is strongly supported by our findings. WBE can also provide precious support in the decision-making process of restriction policies during the epidemic remission phase. Optimization and standardization of laboratory methods should be sought in the short term, so that results from different studies can be compared with reliability.
临床检测粪便中的 SARS-CoV-2 RNA 支持将基于废水的流行病学（WBE）作为 COVID-19 环境监测的宝贵工具的想法。已在几个国家报告了在未经处理的废水中成功检测到 SARS-CoV-2 RNA。本研究调查了在意大利帕多瓦的处理和未经处理的废水中病毒 RNA 的存在和持久性。一个城市的采样点实验网络被用于前瞻性监测活动。
从两个主要的城市废水处理厂系统中选择了七个采样点（即废水泵站、工厂入口和出口）。在两天收集了 11 个随机样本（9 个未经处理，2 个处理过的废水）。所有样品均在 t0 时检测 SARS-CoV-2 RNA，并在 t1（24 小时）时检测其在室温下和冷藏条件下的持久性。总共通过超滤浓缩了 33 个亚样本，并使用两种 RT-qPCR 检测方法对病毒 RNA 的分子检测进行了检测。
在 t0 时，通过至少一种 RT-qPCR 检测方法检测到 4/9 个未经处理的废水样本和 2/2 个三级处理样本呈阳性。估计 SARS-CoV-2 的最低滴度为 4.8-4.9 log10 gc/L。在 t1 时，三个冷藏的亚样本也呈阳性。两种 RT-qPCR 检测方法的灵敏度不同，N 检测法检测到 90%的成功扩增。
在未经处理和处理的废水中检测到了 SARS-CoV-2 RNA。在 4°C 下保存的亚样本中证明了其在 24 小时后的持久性。住院数据表明，WBE 大约每 531 名居民就能检测到 1 例 COVID-19 病例。我们的研究结果强烈支持 WBE 在 COVID-19 环境监测中的作用。WBE 还可以在疫情缓解阶段的限制政策决策过程中提供宝贵的支持。应在短期内寻求优化和标准化实验室方法，以便可靠地比较不同研究的结果。
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