One of the most prominent steps New Castle County took in response to the COVID-19 pandemic was wastewater examination. This proactivity allowed them to keep the pandemic relatively under control. Working with microbiologists at the University of Delaware, the county began monitoring the SARS COV2 virus through wastewater. Dr. Eric Wommack of the University of Delaware had this to say about the process: “the virus, ironically, even though it is a respiratory virus is shed through feces, so it’s very easy to monitor very large populations of people by monitoring the levels of the virus in wastewater.” The county worked in cohorts with the University of Delaware and Duffield Associates to set up CEWER, the Center for Environmental and Wastewater Epidemiology Research. This center allowed them to monitor the virus levels in the county and the University of Delaware dormitories. According to Dr. Wommack, “the earliest of early indicators is wastewater. You see the occurrence of COVID-19 rise in wastewater before you see it in clinical cases.” This makes it one of the better indicators of infection levels and allows officials to react more efficiently.
The general method used to process samples in wastewater testing is sample preparation, sample concentration, RNA extraction, and RNA measurement. When preparing samples, wastewater is collected from the treatment facility and stored at 4 C. The testing process begins when the solution is mixed thoroughly using inversion or mechanical mixing. Finally, large solutes are removed from the solution. When the sample is prepared correctly, ultrafiltration, filtration through an electronegative membrane, Polyethylene Glycol precipitation, skim milk flocculation, or ultracentrifugation can be used to concentrate the samples. After this, a sophisticated extraction method has to be used to obtain highly purified nucleic acid samples and these must be stored at -70 C or below. Finally, SARS COV-2 RNA is quantified using RT-qPCR.
New Castle County was not the only area to utilize this method. In September 2020, the CDC launched the National Wastewater Surveillance System. Internationally, countries like Italy, Spain, Switzerland, the Netherlands, France, and others also use this method. Though this process is useful and efficient to scientists, it has its fair share of problems. The problems that need fixing are: “First, wastewater surveillance cannot provide data in communities and facilities that are not served by municipal sewer systems. Second, interpretation of the results is limited in communities with highly transient populations, such as industrial or tourist regions. Third, the limit of detection for wastewater surveillance (e.g., the fewest infections in a community that can be reliably detected in wastewater) is not well established.” (cdc.gov) If improved upon, wastewater testing can become one of the best tools in overcoming COVID-19 and preventing future pandemics.
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