The Austrian ski resort town of Ischgl, previously noted for its 239 kilometres of groomed lines and lively après-ski scene, was the venue of the first COVID-19 superspreading events in March 2020. A large number of afflicted skiers spread the virus throughout Europe by bringing it back with them.
However, as the epidemic developed, Ischgl was at the forefront for a more positive reason: scientists and health officials in the state of Tyrol were among the first to measure quantities of the pandemic coronavirus in sewage.
Officials were keen to learn whether or not the virus was actually declining so that they might loosen restrictions on travel to the area, which is crucial given the region’s reliance on tourism.
They were also Looking for the Earliest Signs of a Possible Return.
Stefan Wildt, a specialist on wastewater at the state’s department of water management, argues that it was crucial to analyse wastewater since it can take up virus pieces in excrement. More than half of Austria’s population is now part of a nationwide programme, which began in Tyrol and has since extended.
The COVID-19 pandemic has increased the attention paid to wastewater monitoring, which has been used to track polio and other infections for decades. Using the fact that SARS-CoV-2 replicates in the GI tract and is shed in large numbers, frequently before symptoms manifest, the technology is able to detect the virus and eliminate it.
(There is also evidence that the virus can be detected in urine, albeit less reliably.) This may be used to predict where cases might rise and hospitals might become overcrowded, or to monitor illnesses in thousands or millions of individuals without invasive swabs of the nose or throat. In addition, the viral genomic sequences that are shed can give us insight into the virus’s evolutionary history.
In the first study of its kind, researchers from the Netherlands were able to demonstrate that the presence of SARS-CoV-2 virus fragments in wastewater samples was indicative of the prevalence of the virus in the surrounding community (see graphic, below).
Since then, at least 58 nations have initiated SARS-CoV-2 monitoring efforts, as shown by a dashboard developed by Colleen Naughton and her colleagues at the University of California (UC), Merced.
According to Bernd Manfred Gawlik, who is assisting coordinate efforts through the European Commission, 26 of the 27 member countries have complied with the European Union’s recommendation that all member countries develop monitoring systems for SARS-CoV-2 by October 2021.
There are 400 locations in 19 different states that make up the National Wastewater Surveillance System in the United States.
The United States Centers for Disease Control and Prevention (CDC) recently introduced a nationwide dashboard of wastewater data, and on March 2nd, President Joe Biden’s administration said that the monitoring system will be used to help spot new varieties. A programme that started in Bengaluru and has been quite successful is now being rolled out to another half-dozen locations in India.
A Consensus on the Technology’s Usefulness has Yet to be Reached.
Finding a reliable method to quantify virus loads in wastewater presents logistical and technological obstacles, and interpreting the results can be challenging. One example is how a heavy rainstorm might reduce the number of viruses in a city’s wastewater system.
It can take a lot of time and money to set up reliable collection, testing, and reporting mechanisms. Policymakers have acknowledged the value of wastewater monitoring statistics, but few have used them to implement change, instead waiting for the number of cases to climb and the number of patients admitted to hospitals’ intensive care units to increase.
Technical University of Darmstadt researcher Shelesh Agrawal, who has been examining water samples from sites across Germany since 2020, reports that it has been difficult to persuade politicians that the data are relevant. We are the ones responsible for transporting the data. We provide food to your door, but we can’t force you to eat.
Despite having one of the most advanced monitoring systems in the world, researchers in the Netherlands have found that it has had little effect on national policies. In spite of this, local authorities have taken use of the Dutch data, increasing testing in areas where wastewater indicated cases were being overlooked, for instance.
But as the epidemic evolves, wastewater might become a more influential factor in policymaking. Countries are relaxing their pandemic precautions and dropping mandatory population screenings, while an increasing number of individuals depend instead on unreported home tests. Heather Bischel, a wastewater expert from UC Davis, explains why this is the case: “It provides a wider picture image.”
Theoretically, Analysing Wastewater Shouldn’t be too Complicated.
Polymerase chain reaction (PCR) assays are used, just like in conventional clinical tests, to look for targeted fragments of viral RNA in a sample, which are subsequently copied several times to boost the signal. The amount of virus in a sample can be roughly estimated by counting the number of cycles, or rounds of copying, required to detect a signal.
Wastewater samples contain varying amounts of excrement depending on the day and time a sample is obtained, recent rainfall, and whether the upstream toilets are in residences, offices, or other structures, but a throat or nose swab carries about the same quantity of material from person to person.
To properly “read” a sample, all such factors must be taken into account. The outcomes are also affected by how the water is collected, stored, and treated. All of these characteristics make it very difficult to compare data from multiple sites.
“Some of the articles you read make it sound like you scoop some water out, dip a test stick in, and get your response,” says Hannah Safford, a former student in Bischel’s lab at UC Davis and policy expert at the Federation of American Scientists. But it’s a lot more difficult than that.