The aim of this study was to set up a simple protocol to concentrate SARS-CoV-2 from sewage, which can be implemented in laboratories with minimal equipment resources. The method avoids the need for extensive purification steps and reduces the concentration of potential inhibitors of RT-qPCR contained in sewage. The concentration method consists of a single step, in which a small volume (40 mL) of sewage sample is incubated with polyaluminum chloride (PAC)(0.00045 N Al³⁺ final concentration). Virus particles adsorbed to the precipitate are collected by low-speed centrifugation, after which the recovered pellet is resuspended with a saline buffer. PAC-concentrated samples are stable for at least one week at 4 °C. Therefore, they may be sent refrigerated to a diagnosis center for RNA extraction and RT-qPCR for SARS-CoV-2 RNA detection if the lab does not have such capabilities. The PAC concentration method produced an average shift of 4.5-units in quantification cycle (Cq) values compared to non-concentrated samples, indicating a 25-fold increase in detection sensitivity. The lower detection limit corresponded approximately to 100 viral copies per ml. Kappa index indicated substantial agreement between PAC and polyethylene glycol (PEG) precipitation protocols (k = 0.688, CI 0.457−0.919). This low-cost concentration protocol could be useful to aid in the monitoring of community circulation of SARS-CoV-2, especially in low- and middle-income countries, which do not have massive access to support from specialized labs for sewage surveillance.

本研究的目的是建立一个简单的协议来从污水中浓缩 SARS-CoV-2，该协议可以在设备资源最少的实验室中实施。该方法避免了对大量纯化步骤的需要，并降低了污水中含有的 RT-qPCR 潜在抑制剂的浓度。浓缩方法由一个步骤组成，其中将少量 (40 mL) 污水样品与聚合氯化铝 (PAC)(0.00045 N Al ³⁺终浓度）。通过低速离心收集吸附在沉淀物上的病毒颗粒，然后将回收的颗粒重新悬浮在盐水缓冲液中。PAC 浓缩样品在 4 °C 下至少稳定一周。因此，如果实验室没有这样的能力，它们可能会被冷藏送到诊断中心进行 RNA 提取和 RT-qPCR 检测 SARS-CoV-2 RNA。与非浓缩样品相比，PAC 浓缩方法在定量循环 (Cq) 值中产生了 4.5 个单位的平均偏移，表明检测灵敏度提高了 25 倍。检测下限大约相当于每毫升 100 个病毒拷贝。Kappa 指数表明 PAC 和聚乙二醇 (PEG) 沉淀方案之间存在实质性一致性（k = 0.688，CI 0.457−0.919）。