Sewage Smarts Wastewater Monitoring Offers Effective Surveillance of Coronavirus Outbreaks
Robert Delatolla was one of the first to see the Omicron wave rolling toward the Canadian capital of Ottawa. The environmental engineer is a wastewater expert. His team takes samples from the tanks at the sewage treatment plant almost every day and tests them in the laboratory for genetic material from coronaviruses. Up until Dec. 9, his team had found no evidence of the highly contagious variant. Evidence of Omicron first appeared on Dec. 11, and within a week, it was dominant. Since Christmas, he has essentially been finding only elements of the Omicron variant, with elements of the previously dominant Delta variant only making occasional appearances. Those findings are now being borne out in clinical data, Delatolla wrote in an email. His team is also tracking the rise of Omicron in other cities in Canada.
The article you are reading originally appeared in German in issue 2/2022 (January 8th, 2022) of DER SPIEGEL.
"Ottawa wastewater has flipped from all delta to all omicron in about 1 week," his colleague Tyson Graber wrote on Twitter , "This is unprecedented. Alpha took 4 weeks to replace the ancestral variant. Delta took 2 weeks to supplant Alpha." The scientists are proud of their wastewater research – Tyson even describes his job as "cell biologist and poopcaster."
The Ottawa team began using wastewater to monitor the pandemic in April 2020 and they post their measurement data publicly. Officials in Ottawa are currently locked in a bitter debate about whether schools should continue to offer face-to-face instruction despite the Omicron wave, and in the public discussion, the wastewater data are now included as a matter of course. They are quoted in newspapers and taken into account in decisions made by politicians working in health policy.
The situation in Germany is quite different. There is a significant lag here in mapping pandemic developments. How widespread is Omicron in Germany? For a long time, that question couldn't be answered reliably. The official counts from Germany’s center for disease control, the Robert Koch Institute (RKI), rely on the reports of public health offices, which can be inaccurate and out of date.
Recently, the situation has begun clearing up. RKI figures released on Thursday show Omicron levels of 96 percent percent in Bremen, 87 percent in Schleswig-Holstein and 85 percent in Lower Saxony - but below 11 percent in Mecklenburg-Western Pomerania and lower than 30 percent in Saxony and Saxony-Anhalt.
A wastewater sample at a research institute in Berlin's KWB water research centerFoto: Stephanie Pilick / dpa
There are steps that could be taken to speed up monitoring. Shortly before Christmas, a consortium of wastewater researchers announced the first Omicron findings at a few selected measuring points - located in Bavaria, Hesse and North Rhine-Westphalia, for example – but those samples were still preliminary and not particularly reliable. The findings showed Omicron had a share of between 0.4 and 3 percent. Such snapshots show that the principle of wastewater testing works, but since the samples aren’t taken and analyzed systematically or on a nationwide basis, the method isn’t yet suitable for use as a reliable pandemic surveillance system the way it is deployed in Ottawa.
That could soon change. A trio of German ministries – health, environment and education – are currently working together to introduce a national wastewater monitoring system. "The pilot operation is scheduled to start before the end of February 2022 and will initially last until the end of 2022," according to the Education Ministry. The wastewater data could also then be posted on RKI’s public website. The scope of the project is still modest, with 2.9 million euros earmarked for the three different projects that are part of it, but it marks the first steps by the German government to finally comply with a "recommendation" issued by the European Commission almost a year ago for member states to set up wastewater monitoring systems by Oct. 1, 2021.
The advantages of these monitoring and early warning systems are manifold: Virus particles show up in wastewater before infected people even go to the doctor. Experts believe the systems would provide a time advantage of a few days to a week or more. A technical paper by Andreas Tiehm of the German Water Center (TZW) in Karlsruhe published shortly before Christmas assumes a time advantage of almost two weeks.
A biologist preparing sewage samples at a laboratory at the Division of Infectious Diseases & Tropical Medicine at the Medical Center of the University of Munich.Foto: Lukas Barth / REUTERS
The reason is simple: Not everyone who is infected gets tested, but everyone goes to the bathroom. Wastewater testing could become increasingly important, particularly in the current phase of the pandemic, because more and more infections are often proceeding without serious symptoms, argues environment engineer Kyle Bibby, a professor at Indiana’s University of Notre Dame. Although some of those infected may show no symptoms, they could still be contagious, thus fueling the pandemic without realizing it. But the better the clinical testing system, the fewer the benefits of the wastewater monitoring , he says.
Such "silent pandemics" in particular, can be best traced through wastewater in ways that enable officials to act more quickly in affected regions or even only in parts of cities – through mass tests or regional lockdowns, for example. And whereas most of the free tests offered to the public are directly connected to the test subject, wastewater monitoring is totally anonymous. And it also covers people who are just passing through, which could be particularly important in regions with intensive border traffic.
Another advantage is that just a handful of PCR tests is enough to cover hundreds of thousands of people. Such a mass-testing strategy is useful in situations like last summer when infection rates are low and most individual tests are negative, amounting to a considerable waste of money.
That, though, could help explain resistance to wastewater testing, says Bernd Gawlik, who coordinates European wastewater research at the European Commission’s Joint Research Center in Ispra, Italy. Gawlik says PCR labs fear that wastewater testing could drive down the number of lucrative tests that are performed on individuals. "This is nonsense, since the two technologies work in complementarity" he says. Nevertheless, government support for wastewater testing has been sharply diminished due to opposition from laboratories.
Yet it is also true that wastewater-based epidemiology still isn’t fully standardized in the case of SARS-CoV-2. Many factors influence the detection of viral RNA in wastewater. Heavy rainfall, for example, can dilute it in some cases, high oxygen content accelerates the degradation of virus particles and long sewer lines delay the inflow to the extraction point in some cases by more than 30 hours.
Gawlik works tirelessly to merge, match and standardize data from all over the world. He has been in regular contact with the representatives from various EU member states since January and he has invited companies – including airlines, shipping companies, airport operators, water companies and hotels – to a meeting in mid-February. He is hoping that sewage testing can provide an additional safety net for the next travel season.
Gawlik tells the story of a ship that called at the Port of Hamburg, the entire crew of which tested negative for the coronavirus. Testers nevertheless found virus particles in the "black water" from the toilets. By the time the ship entered the next port a few days later, almost the entire crew tested positive.
Testing of wastewater proved years ago to be effective in estimating drug usage. In 2020, Antwerp was Europe’s cocaine capital, as measured by the amount of residue found in wastewater per 1,000 inhabitants, with samples taken in around 80 cities on behalf of the European Monitoring Center for Drugs and Drug Addiction. Amphetamines are particularly popular in Zagreb, Croatia, methamphetamine in Ostrava, Czech Republic, and ecstasy (MDMA) in Amsterdam.
A coffeeshop in Amsterdam: Monitoring wastewater has proven effective in tracking drug usage, among other things.Foto: © Michael Kooren / Reuters/ REUTERS
And testing wastewater has already proven itself in the past to be an extremely useful tool in disease surveillance. The wild polio virus, which causes polio, is considered to have been essentially eradicated around the world, with the exception of isolated places in Afghanistan and Pakistan where it still persists. But in Israel, which has been considered to be polio-free since 1988, researchers suddenly found residue of the polio virus in 2013 in wastewater samples from Negev region. It was the first such find since the establishment of the early warning system in 1989. Officials quickly launched a vaccination campaign and nipped the "silent transmission" in the bud. These days, some 50 countries monitor wastewater in order to detect the circulation of polio viruses at an early stage.
In the final phase of a pandemic, especially, early warning systems that can quickly sound the alarm, but which can also give the all-clear, can become increasingly important – especially during holidays like Easter, when pandemic data only gets compiled days later.
In addition to the wastewater tests, there are also other testing procedures, but they require researchers to rely on the cooperation of numerous volunteers. One such program is run by Dirk Brockman, a physicist at the Institute of Biology at Berlin’s Humboldt University. Since April 2020, he and his team have been evaluating important health data from more than half a million people, all of whom signed up to allow data collected by their fitness wristbands to be transmitted to RKI. Sleeping rhythms, their pulse, the number of steps they take per day: The app collects all that, anonymizes it and then sends it to the researchers.
Initially, the pulse data seemed particularly important: The average resting pulse rate of study participants is 61 beats a minute. An increase of up to three beats on average indicates an infection, possibly because the immune system becomes active, which is strenuous for the body. Statistically, sleep duration also skyrockets by about an hour a day. Duration of sleep only returns to normal after a month.
But now, months later, it appears that the clearest indication of infection is the drastic decrease in daily steps taken. The total drops by more than half for ill people. If the number of daily steps decreases for many people at the same time, infection hotspots can be identified at an early stage – long before health authorities report their figures to RKI.
The Robert Koch Institute's Corona-Datenspende app collects pulses, sleeping patterns and other vital data that can help track and monitor mass infections.Foto: Jens Schicke/ imago images/Jens Schicke
But there’s a disadvantage to these digital measurements: The selection of data donors isn’t representative. Those aged 60 and over, who are particularly at risk, have so far been underrepresented. There are also external factors that can drive up pulses or reduce steps – a summer heat wave, for example. "Above all, however, symptom-free infections remain invisible to the fitness trackers, which is different from the wastewater tests," says Jörg Drewes, a professor of urban water management at the Technical University of Munich.
For the past three decades, the scientist has been researching what bodily excretions reveal about human communities. Germs, cocaine, antidepressants: "Wastewater is a mirror of society," he says.
Last year, Drewes set up a model project together with communities in Berchtesgadener Land, a tourist region in the far southeastern tip of Bavaria. With the usual administrative structures thrown out of whack by the pandemic, Drewes recounts, an opportunity arose to set up an "alternative crisis management" – digital, spontaneous and innovative.
Berchtesgaden with a view of Watzmann Mountain, Germany's second highest peak at 2,713 meters (8,901 feet)Foto:
Lino Mirgeler / dpa
It was inspired by the experiences of the German Armed Forces Medical Service in successfully containing the Ebola epidemic, which broke out in West Africa in 2014. Twice a week, the team took samples at sewage treatment plants and sent them by express delivery to TZW in Karlsruhe to have them analyzed using the PCR method. The incredible finding was that the wastewater samples detected waves of infection rolling in 10 days before official case numbers were available. Drewes is convinced that "this early warning system can serve as a blueprint for other municipalities in Germany."
The wastewater tests also proved to be suitable as a tool for detecting the end of an infection wave, so that the all-clear could be given locally.
Still, all wastewater PCR tests designed to track the spread of Omicron need to be complemented by sequencing, and that’s where the problem lies. Sequencing labs were still on their holiday break even after New Year’s Eve. That is indeed where things break down: Not even the best wastewater testing can help if the laboratories are closed.
And isn’t wastewater monitoring coming a bit too late, anyway, two years after the start of the pandemic? On the contrary, says Drewes. He says the coronavirus could provide a unique opportunity to finally establish nationwide wastewater monitoring in Germany. "We need to be prepared for future epidemics," says the expert. "Think about polio, swine fever and antibiotic-resistant germs. The next pandemic could come as soon as this one is over."