Wastewater-based monitoring of SARS-CoV-2: Insights from small and low-income Brazilian cities
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiological agent of COVID-19, has affected millions of people worldwide and significantly impacted public health. The detection of viral RNA in the feces of infected individuals prompted several countries to adopt wastewater-based epidemiology (WBE) as a tool to monitor SARS-CoV-2 circulation within communities. However, most surveillance studies have focused on large urban centers. This study aimed to analyze the presence and persistence of SARS-CoV-2 in wastewater from two small Brazilian towns with low socioeconomic indicators, limited sewage coverage, and low population density, located in northern Minas Gerais. Wastewater samples were collected biweekly over 12 months, between 2023 and 2024, from three sampling points in Salinas and one in Rubelita. Viral RNA was concentrated using electronegative membranes, and SARS-CoV-2 detection was performed using real-time quantitative polymerase chain reaction. SARS-CoV-2 RNA was detected at all sampling points, with a high frequency of positive samples observed in May, June, October, November 2023, and January 2024. Notably, viral RNA was detected even after the World Health Organization declared the end of the global health emergency on May 5, 2023, and in the absence of officially reported human cases. These findings underscore the value of wastewater surveillance as a tool for monitoring SARS-CoV-2, particularly in areas with limited clinical testing capacity. The study highlights the potential of WBE to detect ongoing viral transmission across diverse urban and socioeconomic contexts, including regions with case underreporting and challenges in mass testing, thereby supporting public health preparedness and response.
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