Most of us, after we flush the toilet, don’t think twice about our body waste. To us, it’s garbage. To epidemiologists, however, wastewater can provide valuable information about public health and help save lives.
History of Wastewater-Based Epidemiology
Wastewater-based epidemiology (WBE) is the analysis of wastewater to monitor public health. The term first emerged in 2001, when a study proposed the idea of analyzing wastewater in sewage-treatment facilities to determine the collective usage of illegal drugs within a community. At the time, this idea to bridge environmental and social sciences seemed radical, but there were clear advantages. Monitoring wastewater is a nonintrusive and relatively inexpensive way to obtain real-time data that accurately reflects community-wide drug usage while ensuring the anonymity of individuals.
This idea was realized in a 2005 study, in which scientists collected sewage water in major Italian cities to estimate local cocaine usage. Traditionally, cocaine usage was estimated using population surveys, consumer interviews, medical records and crime statistics, all of which can be largely biased. The data they obtained from wastewater surveillance was eye-opening, revealing a much higher level of average daily cocaine usage than previously determined. Now, wastewater is used to estimate local drug use in many countries, including cities and universities in the US.
In addition to monitoring drug use, WBE has been used for decades to monitor viral diseases. Viral genetic material can be detected in human feces for days or even weeks before the onset of patient symptoms. This makes wastewater monitoring the perfect early warning system for preventing outbreaks.
In Israel, a wastewater surveillance program to monitor polio outbreaks has been in place since 1988, which involves monthly sampling of 8–10 sewage treatment facilities in populated areas. In 2013, the polio virus suddenly reappeared in sewage water, alerting health officials to initiate a nationwide vaccination campaign. Because of the early warning, a potentially disastrous outbreak was prevented. Other recent studies demonstrated how wastewater can be used to detect various strains of norovirus and hepatitis viruses.
WBE for Tracking COVID-19
Fast forward to 2020, the COVID-19 pandemic caused by the novel coronavirus SARS-CoV-2 has further propelled WBE into the spotlight. Many believe that sewage surveillance is the most practical way for long-term monitoring of SARS-CoV-2 outbreaks. This approach is more cost-effective compared to large-scale diagnostic testing and can detect the virus even before symptoms have occurred, meaning public health officials can be proactive rather than reactive when controlling outbreaks.
Several municipalities have already begun monitoring sewage for the presence of SARS-CoV-2 viral RNA. Since 2018, a group at Arizona State University has been monitoring wastewater for opioid use in the city of Tempe, Arizona, and the data is released through a public-facing dashboard that reports the levels of four common opioid drugs. This experience has allowed them to quickly respond to the pandemic by creating a COVID-19 dashboard that provides the overall infection trend of 185,000 residents in seven areas within the city. Other states, including Utah and Montana, are following suit.
A major challenge in using wastewater for SARS-CoV-2 detection is the lack of an approved standardized analytical method, which typically take years to achieve. However, scientists in organizations around the world (including Promega) are sharing their protocols and collaborating to provide solutions.
Development of Viral RNA Detection Methods
The PCR-based method commonly being used for detecting viral RNA in wastewater is very similar to what is used in clinical or research labs. However, the complexity of wastewater samples brings some additional challenges, such as the presence of PCR inhibitors. Therefore, the viral RNA purification method is crucial for successful detection. Scientists at Promega have developed protocols specifically for detecting SARS-CoV-2 RNA in wastewater, using either a precipitation method or centrifugal filtration method. In an interview with GenomeWeb, Promega Global Commercialization Marketing Manager, Brigitta Saul, states that Promega’s “expertise on the design of nucleic acid purification systems and formulating PCR master mixes tolerant of inhibitors commonly found in environmental samples allows us to design and formulate workflow solutions that are able to cope with these kinds of samples.” Currently, the PureFood GMO and Authentication Kit provides effective purification of viral RNA from wastewater samples. The kit is compatible with the Maxwell® Instruments, which can automatically process up to 48 samples at once.
Promega scientists have also developed a new RT-qPCR kit specific for SARS-CoV-2 viral RNA detection in wastewater. The kit includes primers and probes to detect SARS-CoV-2 as well as amplification controls. Not only can this viral RNA kit isolate single samples using manual extraction, but it can also be adapted to high-throughput automated RT-qPCR detection. Another kit for viral concentration and TNA extraction from wastewater samples is currently under development (contact email@example.com for more information).
As methods for detecting viral RNA in wastewater continue to advance, there is hope that WBE programs will be implemented globally to help control and prevent outbreaks of COVID-19 as well as future viral diseases.
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