Wastewater testing: COVID-19 earliest warning system

Environmental chemist reviews new wastewater surveillance method that provides rapid detection of the COVID-19 virus
February 25, 2021

With new variants being reported every day, refining methods to rapidly detect the spread of COVID-19 at a large scale is needed. Research now shows the disease can be detected in feces within three days of infection, which is much sooner than the time it takes for people to develop symptoms and get an official diagnosis.

In a new paper in the journal Environmental Chemistry Letters, internationally renowned environmental chemist Virender Sharma, PhD, of the Texas A&M University School of Public Health, reviews a new surveillance method that relies on biomarkers in wastewater to detect the presence of SARS-CoV-2 (the virus that causes COVID-19) in a community. This new methodology can give public health officials a heads up on disease outbreaks and show where additional clinical testing and other resources are most needed. Such an approach is particularly helpful in areas that may not have enough resources to perform large-scale clinical testing.

Although SARS-CoV-2 is transmitted mainly by person-to-person contact and airborne droplets and aerosols, the virus and its genetic material are also excreted through urine and feces. SARS-CoV-2 has been found in wastewater around the world, meaning that monitoring sewer lines and wastewater treatment facilities can help public health officials rapidly identify locations where COVID-19 outbreaks are occurring. However, researchers are still determining the best ways to quickly and accurately detect SARS-CoV-2 in wastewater.

Sharma and colleagues outlined the wastewater disease surveillance process and identified questions that must be answered. The surveillance process involves sampling and concentrating wastewater, extracting ribonucleic acid (RNA) from the virus, detecting the genetic signature of SARS-CoV-2 and determining the severity of the outbreak based on what has been identified in the wastewater. The first step is crucial as the methods used to collect samples, the amount of time between sampling and detection and even sample storage conditions like temperature can affect results. The presence of organic matter and suspended solids in wastewater and the process of concentrating samples from a large volume of wastewater can also influence the results.

After collecting and concentrating samples of potentially virus-laden wastewater comes extracting viral RNA. Sharma and colleagues note that this calls for a procedure that can break apart virus particles without damaging the virus’s genetic material. RNA extraction in wastewater is further complicated by the presence of substances in wastewater that can react with and damage RNA or that viral RNA could stick to. Because of this, researchers must find an optimal extraction method, which could vary based on wastewater properties. Once viral RNA has been successfully extracted, researchers can then adapt a technique used in clinical testing known as quantitative reverse transcription polymerase chain reaction.

Although vaccines for COVID-19 are currently being administered, containing SARS-CoV-2 remains crucial. Wastewater surveillance holds promise for better detection of the virus, aiding containment efforts. Additionally, the lessons learned from honing wastewater disease surveillance for COVID-19 can inform efforts to detect other disease outbreaks early, relatively easily and at a large scale. Once thought of as unwanted material to get rid of, wastewater is now a valuable source of public health information that can slow the spread of disease.

— Rae Lynn Mitchell

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