International Journal of Environmental Research and Public Health Article Detection of SARS-CoV-2 in Wastewater Northeast of Mexico City: Strategy for Monitoring and Prevalence of COVID-19 José Roberto González-Reyes 1 , María de la Luz Hernández-Flores 2,*, Jesús Eduardo Paredes-Zarco 1 , Alejandro Téllez-Jurado 3 , Omar Fayad-Meneses 2 and Lamán Carranza-Ramírez 2 1 Investigación Aplicada para el Bienestar Social y Ambiental Asociación Civil (INABISA A.C.), Pachuca 42088, Mexico; [email protected] (J.R.G.-R.); [email protected] (J.E.P.-Z.) 2 Consejo Ejecutivo del Complejo Científico y Tecnológico Sincrotrón, San Agustín Tlaxiaca 42163, Mexico; [email protected] (O.F.-M.); [email protected] (L.C.-R.) 3 Laboratorio de Agrobiotecnología, Universidad Politécnica de Pachuca, Carretera Pachuca-Cd. Sahagún km 20, Zempoala 43830, Mexico; [email protected] * Correspondence: mariadelaluz.fl[email protected] Abstract: A month-long wastewater sampling project was conducted along the northeast periphery of Mexico City, specifically in the state of Hidalgo, to assess the presence of SARS-CoV-2. To deter- mine the prevalence of infection and obtain a range of COVID-19 cases in the main metropolitan zones. Viral RNA residues (0–197,655 copies/L) were measured in wastewater from the five central municipalities in the state. By recording the number of RNA viral copies per liter, micro-basins delim- Citation: González-Reyes, J.R.; itation, demographic and physiological data, an interval of infected people and virus prevalence was Hernández-Flores, M.d.l.L.; estimated using a Monte Carlo model (with 90% confidence) in the micro-basin of five municipalities Paredes-Zarco, J.E.; Téllez-Jurado, A.; with metropolitan influence or industrial activity. Our procedure determined that the percentage Fayad-Meneses, O.; Carranza-Ramírez, of the infected population ranges from 1.4% to 41.7%, while the official data reports 0.1–0.3%. This L. Detection of SARS-CoV-2 in model is proposed as a helpful method of regional epidemiological monitoring through the analysis Wastewater Northeast of Mexico City: Strategy for Monitoring and of viral prevalence. Prevalence of COVID-19. Int. J. Environ. Res. Public Health 2021, 18, Keywords: environmental policy; wastewater-based epidemiology (WBE); wastewater; epidemiological 8547. https://doi.org/10.3390/ monitoring; prevalence ijerph18168547 Academic Editors: Carla Viegas and Elisabete Carolino 1. Introduction Since the detection of a new type of SARS-COV-2 virus in the city of Wuhan, China, Received: 8 June 2021 prevalent studies of different types have been carried out by [1,2]. The use of wastewaters Accepted: 8 August 2021 in prevalence was conducted first for SARS-CoV and MERS-CoV [3], since prevalence is a Published: 13 August 2021 metric that accurately tracks the behavior of a pandemic. The SARS-CoV-2 virus is the etiological agent of coronavirus disease 2019 (COVID-19). Publisher’s Note: MDPI stays neutral Because the virus uses the angiotensin converting enzyme (ACE2) as a receptor to enter with regard to jurisdictional claims in human cells [4] and there is high expression of ACE2 messenger RNA in the gastrointestinal published maps and institutional affil- system ([5–7]). This evidence supports the possibility of SARS-CoV-2 replication in the iations. gastrointestinal tract [8]. Some clinical studies reported prolonged fecal shedding of SARS-CoV-2 RNA for up to seven weeks after the first onset of symptoms ([6,9]) or other body fluids [10]. Another study reported that viral RNA could be detected in stool in 81.8% of cases [11]. Copyright: © 2021 by the authors. Keeping in mind that there is scientific evidence of the detection of viable SARS- Licensee MDPI, Basel, Switzerland. CoV-2 in feces of patients with COVID-19 ([9,12]) and the presence of virus RNA in This article is an open access article wastewater ([1,13]), it is necessary to create methods using wastewater as a possible source distributed under the terms and of information for epidemiological studies and its risks to human health [8]. The presence conditions of the Creative Commons of SARS-CoV-2 in wastewater samples is already confirmed by studies from different Attribution (CC BY) license (https:// × creativecommons.org/licenses/by/ countries ([1,9,13]). To quote an example, “Viral loads of up to 1.9 104 copies/L have 4.0/). Int. J. Environ. Res. Public Health 2021, 18, 8547. https://doi.org/10.3390/ijerph18168547 https://www.mdpi.com/journal/ijerph Int. J. Environ. Res. Public Health 2021, 18, 8547 2 of 14 been detected in wastewater in locations close to departments receiving COVID-19 patients in Wuhan, China [14]”. The presence of SARS-CoV-2 viral RNA in wastewater makes it possible to utilize it as a surveillance tool for invasion, prevalence, molecular epidemiology, and possible eradication of the virus in a community [8]. For example, ([13]) reported the prevalence level of SARS-CoV-2 by measuring the viral RNA copies quantified by the RT-qPCR technique found from sewage in a basin of Australia. The wastewater surveillance and Monte Carlo data suggested a measure of the prevalence of SARS-CoV-2 infection of 9.6% in the studied basin over six days. The increasing severity of the pandemic could be related to the lack of adequate testing trials to quickly and accurately identify patients infected with SARS-CoV-2 [15]. In addition, asymptomatic and pre-asymptomatic SARS-CoV-2 infected patients are highly contagious and, given the lack of appropriate screening assays, many SARS-CoV-2 infected patients have had contact with uninfected individuals before being identified for home isolation or hospitalization [16]. Wastewater-based epidemiology of human viruses can be a useful tool for population-scale monitoring of SARS-CoV-2 prevalence and epidemiology to help prevent further spread of the disease, particularly within urban centers [17]. This study aimed to analyze SARS-CoV-2 viral residues in wastewater from 5 mu- nicipalities found in metropolitan areas (Pachuca de Soto, Mineral de la Reforma, Tula de Allende, Tizayuca and Tepeapulco) of the great importance of the State of Hidalgo (northeast of Mexico City). Through its detection and quantification using the RT-qPCR technique for modeling the results using the Monte Carlo model to estimate the number of infected people in the study areas and the prevalence of SARS-CoV-2. 2. Case Study The study area was limited to five municipalities located northeast of Mexico City, in the State of Hidalgo, where five central metropolitan municipalities were chosen: Pachuca de Soto, Mineral de la Reforma, Tula de Allende, Tizayuca, and Tepeapulco. These munici- palities are home to an essential proportion of the total population of the State of Hidalgo. For practical terms, these five municipalities have been named as follows, respectively: “Municipality in the Main Metropolitan Area of the State of Hidalgo (MMHS)”, “Munici- pality on the East Side of the Main Metropolitan Area of the State of Hidalgo (MEMHS)”, “Municipality in the West with Predominant Food and Chemistry Industry (MWFC)”, “Municipality in the North of Mexico City Metropolitan Area (MNMC)” and “Municipality in the East with Predominant Metal-Mechanic Industry (MWFC)”. Data number of infected and the population for the year 2020 and the place taken at the state level are presented in Table1. Table 1. COVID-19 cases in municipalities where the sampling sites are located. Municipality Place in Hidalgo State Confirmed Infected According to the Number of People Reported by the Municipality Municipality Sampling Date 2 Confirmed Infected People Government at Sampling Dates 1 Population in 2020 Reported by the Government 1 319 June 30th (S1) MEMHS 2nd place 187,701 347 July 7th (S2) 848 June 30th (S1) MMHS 1st place 281,702 959 July 7th (S2) 124 June 30th (S1) MWFC 2 9th place 117,083 142 July 7th (S2) 158 June 30th (S1) MEMI 6th place 55,061 177 July 7th (S2) 283 June 30th (S1) MNMC 3rd place 140,727 321 July 7th (S2) 1 Data reported by the health sector agencies in collaboration with the Federal Government on the website: https://coronavirus.hidalgo. gob.mx/[ 18] accessed on 7 July 2021. June 2nd 30th sampling is represented by S1, while July 7th sampling is represented by S2. 2 MWFC include: MWFC, MWFC 2 and MWFC 3. Int. J. Environ. Res. Public Health 2021, 18, x FOR PEER REVIEW 3 of 14 321 July 7th (S2) 1 Data reported by the health sector agencies in collaboration with the Federal Government on the website: https://corona- Int.virus.hidalgo.gob.mx/ J. Environ. Res. Public Health [18]2021 accessed, 18, 8547 on 7 July 2021. June 2nd 30th sampling is represented by S1, while July 7th sampling3 of 14 is represented by S2. 2 MWFC include: MWFC, MWFC 2 and MWFC 3. In all the municipalities studied, a hospital called “COVID HOSPITAL” consists of existingIn hospitals all the municipalities with new infrastructure, studied, a hospital specifically called “COVID for COVID-19 HOSPITAL” patients’ consists treatment. of existing hospitals with new infrastructure, specifically for COVID-19 patients’ treatment. In most sampling points, the samples contained wastewater coming from any COVID In most sampling points, the samples contained wastewater coming from any COVID HospitalHospital to to guarantee guarantee the the SARS-CoV-2 SARS-CoV-2 viral loadload in the samples. Figure1 1shows shows the the loca- tionlocation of sampling of sampling points points in the in thenortheast northeast of ofMexico Mexico City. City. FigureFigure 1. Study 1. Study area area and and sampling sampling site ofof five five municipalities municipalities of theof the State State of Hidalgo. of Hidalgo. 3. 3.Materials Materials and and Methods Methods 3.1.