Water testing
During the COVID-19 pandemic, testing sewage for viral RNA provided an early warning of outbreaks when clinical testing missed many cases.
Now, as communities monitor sewage for everything from SARS-CoV-2 to polio and drug residues, a debate emerges: should water companies be required to conduct continuous wastewater epidemiology?
Advocates argue that round-the-clock sewage surveillance could transform disease detection and environmental protection, while others caution about practical challenges.
This feature explores emerging trends in WBE, technological advances in wastewater monitoring, and stakeholder perspectives on mandating continuous surveillance.
Long before COVID-19, scientists had tapped sewers for clues about community health.
For decades, public health programs monitored sewage for poliovirus circulation as part of eradication efforts, and researchers analysed wastewater to compare illicit drug use in different cities.
However, it was the pandemic that truly thrust WBE into the limelight.
“After being around for more than 15 years, wastewater-based epidemiology is finally getting the attention it deserves, thanks in no small part to the challenges brought about by the COVID-19 pandemic,” said Professor Rolf Halden, an early WBE pioneer.
During 2020, numerous countries launched sewage surveillance for SARS-CoV-2.
In the UK, national programmes in England, Scotland and Wales began regularly analysing wastewater at treatment works as an early warning system for COVID spikes.
In the U.S., the CDC created the National Wastewater Surveillance System (NWSS) in late 2020, which has grown to include over 1,200 testing sites monitoring wastewater for pathogens – covering roughly 130 million people.
Across Europe as well, “most countries in the European Union have established regular wastewater surveillance in their cities after the beginning of the COVID-19 pandemic”.
Not all regions have embraced WBE.
A recent study noted that countries like Japan still only have pilot programs in a handful of cities (fewer than 20) and remain hesitant to adopt national wastewater surveillance.
Nonetheless, global initiatives are underway to promote WBE.
In mid-2025 an international network called Wastewater Surveillance for Pandemic Prevention (WaSPP) was launched, backed by academia, NGOs, and industry partners across Africa, Asia, and Europe.
Their goal is to standardise methods for sewage monitoring of high-risk viruses – from coronaviruses to Ebola – as an early warning system for the next pandemic.
“Wastewater testing offers a sensitive, cost-effective tool for surveillance that could identify these infections… giving us a better chance at preventing future pandemics,” explains Professor Nicholas Grassly of Imperial College London.
Traditional wastewater epidemiology has relied on periodic sampling – for example, collecting 24-hour composite samples once or twice a week and sending them to labs for analysis.
Continuous monitoring, by contrast, envisions ongoing, high-frequency data collection from sewage in near real-time.
Recent technological advancements are rapidly closing the gap to make this possible.
Many programs still use laboratory-based RT-qPCR to quantify genetic material of viruses (like SARS-CoV-2) in wastewater samples.
These methods are sensitive, but sample processing and lab turnaround can take days, limiting how “continuous” the data flow is.
Emerging “smart sewer” technologies aim to automate and speed up detection.
Researchers are developing biosensors that can be deployed at treatment plants or in sewers to detect pathogens on-site.
Such sensors – often electrochemical or optical – can transmit data wirelessly in real-time.
A 2023 review highlighted that biosensors offer high sensitivity and specificity and can deliver rapid results without the need for complex lab work, making them promising for real-time WBE.
These devices, integrated via the Internet of Things (IoT), could enable a network of continuous monitors feeding data to public health dashboards.
For instance, startup companies have prototyped portable instruments that replace lab tests with field-deployable devices capable of detecting bacteria and viruses down to single-digit copies per millilitre.
While such technology is still maturing (and may have limitations in sensitivity at low infection levels), it points toward a future where utilities might have automated pathogen sensors running 24/7.
Another trend powering continuous surveillance is genomic sequencing of wastewater.
Beyond simply detecting known targets, advanced labs are performing metagenomic sequencing on sewage samples to screen for a multitude of pathogens and even novel organisms.
This approach has already proven its worth: in late 2021, scientists detected signatures of the Omicron variant in community wastewater before any clinical cases were confirmed locally.
Continuous sequencing surveillance could similarly catch other emerging threats (such as new flu strains or antibiotic-resistant “superbugs”) early in their spread.
The UK Health Security Agency’s latest £1.3m investment is exploring “cutting-edge technologies to improve the UK’s ability to detect and identify the genetic material of various viruses in wastewater, tracking how the amount of virus detected changes over time”.
This development programme, announced in 2025, will build on existing polio sewage surveillance and test the feasibility of an early warning system for pathogens like Mpox, West Nile virus, and Lassa fever via wastewater signals.
It’s clear that both the tools and the scope of wastewater monitoring are expanding rapidly.
Proponents of continuous wastewater epidemiology say the benefits to public health are too great to ignore.
First and foremost is early detection.
Wastewater acts as a pooled sample of an entire community – people start shedding pathogens (viruses, bacteria) in stool and urine often before they show symptoms (if they ever do).
This means surges of infection show up in sewage days or weeks ahead of clinical case spikes.
As Michelle Clements, Public Relations Manager at Portland Water District in Maine, observed about their monitoring program: “Over time, it has really indicated trends before you see them clinically”.
This early-warning capacity allows health agencies to respond faster – for example, by mobilising pop-up testing or vaccination clinics in areas with rising wastewater signals.
It can also tip off hospitals to prepare for an influx of patients.
During the pandemic, such data guided interventions by identifying hotspots of COVID-19 transmission even when official case counts were low due to testing gaps.
Continuous sewage monitoring is also comprehensive and unbiased.
Unlike clinical surveillance, it doesn’t depend on people showing up for tests or reporting symptoms.
“Wastewater surveillance may detect pathogens within the community regardless of individual symptom status… capturing asymptomatic infections,” notes the Texas Department of State Health Services.
Every flush is essentially an anonymous sample, so the data covers everyone connected to the sewer system, cutting across demographics and healthcare access.
The Rockefeller Foundation’s Pandemic Prevention Institute emphasises that a single sewage sample can reflect the health of thousands of people “for a fraction of the cost of clinical tests”.
In fact, WBE has been demonstrated to be highly cost-effective.
One university study found monitoring certain public health metrics via wastewater was 200 times cheaper than doing equivalent surveys and clinical tests – just $0.58 per person via sewage analysis versus $127 per person using traditional methods.
Continuous monitoring could leverage this efficiency, turning what used to be an expensive undertaking (mass individual testing) into a routine utility function.
As Durk Krol, Executive Director of Water Europe, put it: wastewater surveillance is an “alternative approach, independent of costly individual tests, for large-scale surveillance… at a fraction of the cost”.
There are clear environmental protection angles to expanding wastewater monitoring as well.
Sewage doesn’t only carry viruses from humans – it also contains chemical pollutants, drug residues, and antibiotic-resistant bacteria that can impact ecosystems.
By continuously scanning wastewater, utilities and regulators could catch toxic substances or illegal discharges early and trace their sources.
Moreover, the data can highlight when standard treatment isn’t eliminating microbial hazards.
A 2024 report by the UK Royal Academy of Engineering pointed out that even treated sewage can contain high levels of faecal microbes and that routine release of these organisms into rivers poses public health risks.
The report called for accelerating “continuous water quality monitoring for microbiological organisms” in wastewater effluent to better protect bathers and downstream users.
Continuous epidemiological monitoring could dovetail with such environmental monitoring – for instance, by tracking antimicrobial resistance (AMR) genes in wastewater.
Public health engineers note significant concern about the rise of AMR in sewage, as human pathogens with antibiotic resistance can proliferate and spread via discharge into the environment.
The WBE approach could serve as a sentinel for emerging AMR hotspots, informing both healthcare and environmental mitigation.
Indeed, the tools pioneered for pathogen surveillance can be applied to gauge the prevalence of antibiotic resistance, as well as community exposure to chemicals like pharmaceuticals or pesticides.
In this way, continuous wastewater epidemiology supports a One Health perspective – recognising that human health, environmental quality, and microbial ecology are interconnected.
Water utilities themselves are increasingly seeing the value in wastewater surveillance – provided it is done with clear purpose and support.
At Portland Water District (PWD) in the US, wastewater staff began SARS-CoV-2 monitoring in mid-2020 and have since expanded to track other viruses like influenza, RSV, and even monkeypox in sewage.
“It’s a great public service,” said Scott Firmin, PWD’s Director of Wastewater Services. “We’re part of this community, and this is another way we can add value to our customers in an unexpected way.”
His utility collects thrice-weekly samples and ships them to public health labs; the results go to the state CDC for interpretation and action.
Importantly, PWD’s participation has been grant-funded – federal and philanthropic funds cover the costs, so it hasn’t burdened the utility’s ratepayers.
With this support, operators only needed to make minor scheduling adjustments to integrate the sampling, which Firmin calls “a worthwhile cause”.
The experience in Portland highlights a key point: partnerships between utilities and health agencies can make continuous WBE feasible.
The Texas DSHS explicitly “partners with local health departments and water utilities” on its wastewater surveillance program, emphasising that such collaboration helps communities prepare and act on disease trends.
Many utilities view their role as providing the sample and technical access, while public health experts handle data analysis and communication.
As Firmin noted, “We have a public health role, [but] it’s not taking this type of information and getting community action” – that is left to health authorities.
Utilities fulfilling their mission to protect public health is not new – they already ensure drinking water safety and compliant wastewater treatment.
Continuous epidemiological monitoring could become another expected service, especially if external funding or regulations mandate it.
Public health researchers and agencies are some of the strongest champions for continuous wastewater monitoring.
Professor Steven Riley, the UKHSA’s Director General of Data and Analytical Sciences, argues that “Wastewater monitoring has the potential to be central to our work on pathogens that threaten public health.
It shows great promise as a cost-effective way for us to quickly detect a range of emerging pathogens, which is vital for an effective response.”
During the pandemic, many in public health came to trust sewage data as an unbiased reflection of community infection levels.
In a Rockefeller Foundation survey of U.S. health departments, there was “large consensus around the unique advantages of this innovative data source: that it doesn’t rely on individual testing, may act as an early warning system, captures asymptomatic infections, and can be used to monitor viral variants”.
Groups like the Association of Public Health Laboratories (APHL) and CDC have been building networks and toolkits to sustain wastewater surveillance beyond COVID.
The U.S. National Academies even convened an expert panel, resulting in a 2023 report on “Wastewater-based Disease Surveillance for Public Health Action” – a sign that the scientific community views this as a long-term component of disease monitoring.
Many public health voices now call for integrating wastewater data into routine disease surveillance systems (for diseases like influenza, norovirus, polio, etc.), rather than treating it as an ad-hoc experimental tool.
Academia and NGOs are likewise advocating for expanded use of WBE.
The Rockefeller Foundation’s Pandemic Prevention Institute has actively promoted wastewater surveillance globally as an equity-focused tool.
Because sewage surveillance inherently covers entire communities, it can reveal health issues in marginalised populations that might be missed by clinical reporting.
Rockefeller notes that the data provide “a more equitable view of population health, equipping policymakers with powerful data to advocate for public health resources that protect all”.
Environmental NGOs are also weighing in, albeit from a water quality angle.
In the UK, for example, campaigns by groups like Surfers Against Sewage have drawn attention to pathogens in sewage-polluted bathing waters, indirectly bolstering the argument that continuous microbial monitoring is needed for public safety.
There is also emerging discussion about ethics and privacy by civil liberties NGOs – ensuring that wastewater data, which is aggregate, remains used solely for public health and not to target specific communities.
Notably, WBE is typically privacy-preserving since it cannot pinpoint individuals; as one report put it, the methodology “raises few ethical concerns as individuals cannot be identified” in population-level sewage data.
Even so, experts urge transparency with the public about what is being monitored in their wastewater and why, to maintain trust in these programs.
With broadening interest in WBE, should regulators require water companies to perform continuous wastewater epidemiology?
Proponents say yes – making it mandatory would ensure this powerful tool is universally and consistently applied, rather than patchy.
They argue that routine surveillance saves lives by enabling faster outbreak responses and guiding public health interventions.
For example, continuous sewage data could flag a resurgence of polio or the introduction of a novel virus in a city, prompting vaccination or other measures before hospitals fill up.
During COVID-19, wastewater data sometimes gave a weeks’-advance notice of case waves.
In the context of biothreats, early containment can avert exponential spread and heavy societal costs.
Economically, the cost of ongoing monitoring is minor compared to the cost of uncontrolled outbreaks or to the baseline operations of water utilities.
WBE also provides knowledge beyond infectious diseases. It can reveal trends in community health behaviours (e.g. opioid or alcohol use trends, as shown by WBE studies), allowing targeted public health campaigns.
Making it a regular requirement could spur innovation and efficiency.
If every utility needed to monitor continuously, it would drive demand for automated sampling instruments, cheaper assays, and bioinformatics tools to manage the data.
Over time, this could bring down costs further and improve standardisation of methods.
On the other hand, critics and cautious voices urge careful consideration before imposing a mandate.
One concern is the practical and financial burden on water firms.
Not all utilities have laboratories or epidemiologists on staff; requiring continuous pathogen monitoring could force them to significantly expand capabilities or outsource to labs.
Smaller or rural utilities in particular may struggle.
A national survey in the U.S. found that among local health agencies that hadn’t yet tried wastewater surveillance, only 7% felt they had the resources needed to start.
Without dedicated funding, a mandate could be seen as an unfunded liability for utilities.
There are calls for governments to provide sustained funding or at least to funnel the data collection into centralised programs (similar to how, in the U.S., CDC’s NWSS supports states and localities with lab testing and analysis tools).
Another challenge has been data interpretation and integration. Collecting sewage data is one thing; acting on it is another.
Early in the pandemic, many local officials were unsure how to translate viral RNA copies per liter of sewage into policy decisions.
If continuous monitoring becomes routine, agencies will need clear guidelines: e.g. what thresholds of pathogen load trigger alerts, how to combine wastewater trends with clinical data, etc.
Developing these decision frameworks is still a work in progress.
There is also the issue of data overload – continuous sensors could generate massive data streams.
Health departments will require new analytics to distil meaningful signals from noise (for instance, differentiating a true uptick in pathogen circulation from a temporary spike due to rainfall dilution or lab variability).
Privacy and trust issues, while generally minimal for community-level surveillance, should be acknowledged.
Ethicists note that if wastewater monitoring becomes extremely granular (e.g. sampling from specific neighbourhoods or buildings), it could stigmatise those communities if data are not handled sensitively.
For instance, publishing that “neighbourhood X has the highest cocaine metabolites in wastewater” or “dorm Y has SARS-CoV-2 RNA detected” can raise social and ethical questions.
Thus, some argue that any mandate should include governance on data privacy and use – ensuring results are reported in ways that benefit public health without harming community trust.
Finally, the question of necessity is debated.
Do we need continuous surveillance at all times, or only during outbreaks?
Opponents of a strict mandate might say routine monitoring for every possible pathogen could be overkill when a community is not facing any known threat.
They suggest a risk-based approach: maintain readiness to scale up sewage testing when needed (for example, test continuously during winter flu season or if an unusual disease is detected in the region).
However, proponents counter that the very nature of emerging threats is you don’t know when or where they will arise – continuous broad surveillance is like maintaining smoke detectors; you hope to never hear an alarm, but you’ll be glad it’s there in case of fire.
In the words of one water industry veteran, ongoing sewage epidemiology “elevates the importance of wastewater… and is information that we can’t get otherwise”. It transforms passive infrastructure into an active public health sentry.
The momentum behind wastewater epidemiology suggests that continuous monitoring by water firms could soon become a new normal.
Across the globe, stakeholders from professors to public health chiefs are converging on the idea that our sewers can serve as sentinels – catching the first hints of danger, whether that’s a virus on the move, a spike in drug misuse, or antimicrobial threats brewing.
Crucially, continuous wastewater surveillance embodies a preventive, data-driven approach to health and environmental protection.
It shifts some focus from responding to crises to anticipating them.
“Our first responsibility is to keep people safe,” noted UK minister Pat McFadden at the launch of a wastewater monitoring project, calling the approach “a valuable tool in our armoury – helping us prepare for and rapidly detect future outbreaks”.
Moving forward, if continuous wastewater epidemiology is to be required of water companies, the frameworks must be supportive.
Funding and training need to accompany any mandates so that even smaller utilities can participate effectively.
Clear protocols and objectives (what to test for, how often, and how to act on the data) should be established, ideally informed by national health agencies so that data from different regions can be compared and aggregated.
When done right, the rewards are significant: a safer public, empowered by the knowledge flowing under our feet, and water utilities recognised not just as providers of clean water but as guardians of community health.
As one UK engineer observed, the 19th-century investment in wastewater systems eliminated cholera and saved countless lives; now it’s time for a 21st-century vision – one where smart sewers and continuous surveillance help safeguard public health in an ever-changing world.
IET 36.3 May
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