Quantification of SARS-CoV-2 in urban wastewaters has emerged as a cheap, efficient strategy to follow trends of active COVID-19 cases in populations. Moreover, mathematical models have been developed that allow the prediction of active cases following the temporal patterns of viral loads in wastewaters. In Mexico, no systematic efforts have been reported in the use of these strategies. In this work, we quantified SARS-CoV-2 in rivers and irrigation canals in the Mezquital Valley, Hidalgo, an agricultural region where wastewater from Mexico City is distributed and used for irrigation. Using quantitative RT-PCR, we detected the virus in six out of eight water samples from rivers and five out of eight water samples from irrigation canals. Notably, samples showed a general consistent trend of having the highest viral loads in the sites closer to Mexico City, indicating that this is the main source that contributes to detection. Using the data for SARS-CoV-2 concentration in the river samples, we generated a simplified transport model that describes the spatial patterns of dispersion of virus in the river. We suggest that this model can be extrapolated to other wastewater systems where knowledge of spatial patterns of viral dispersion, at a geographic scale, is required. Our work highlights the need for improved practices and policies related to the use of wastewater for irrigation in Mexico and other countries.

量化城市废水中的 SARS-CoV-2 已成为一种廉价、有效的策略，可以跟踪人群中活跃的 COVID-19 病例趋势。此外，还开发了数学模型，可以根据废水中病毒载量的时间模式预测活跃病例。在墨西哥，在使用这些策略方面没有系统性努力的报告。在这项工作中，我们量化了伊达尔戈梅斯基塔尔谷河流和灌溉渠中的 SARS-CoV-2，这是一个农业区，墨西哥城的废水被分配并用于灌溉。使用定量 RT-PCR，我们在八分之六的河流水样和八分之五的灌溉渠水样中检测到病毒。尤其，样本显示出在靠近墨西哥城的地点具有最高病毒载量的普遍一致趋势，表明这是有助于检测的主要来源。使用河流样本中 SARS-CoV-2 浓度的数据，我们生成了一个描述病毒在河流中扩散的空间模式的简化传输模型。我们建议该模型可以外推到其他废水系统，在这些系统中，需要了解地理范围内病毒传播的空间模式。我们的工作强调了在墨西哥和其他国家需要改进与废水用于灌溉相关的实践和政策。我们生成了一个简化的传输模型，该模型描述了病毒在河流中扩散的空间模式。我们建议该模型可以外推到其他废水系统，在这些系统中，需要了解地理范围内病毒传播的空间模式。我们的工作强调了在墨西哥和其他国家需要改进与废水用于灌溉相关的实践和政策。我们生成了一个简化的传输模型，该模型描述了病毒在河流中扩散的空间模式。我们建议该模型可以外推到其他废水系统，在这些系统中，需要了解地理范围内病毒传播的空间模式。我们的工作强调了在墨西哥和其他国家需要改进与废水用于灌溉相关的实践和政策。