Skiers the world over have visited or heard of Tyrol, Austria. The state, located in the Alps, is home to folk traditions, historic sites, and ski resorts. The advent of SARS-CoV-2, the virus that causes COVID-19, coupled with high numbers of tourists visiting the resorts, produced what is known as one of the first superspreader events of the pandemic.
Superspreader events happen when a contagious individual infects an unusually high number of other people. And that's what happened in February 2020 in Tyrol: Small numbers of visitors carrying the virus infected many others. When the afflicted tourists returned home, they brought photos, souvenirs, and stories to tell. Many also brought the SARS-CoV-2 virus with them.
The state of Tyrol thrives due to its tourism industry. Scientists from the region were among the first group of experts looking for levels of the SARS-CoV-2 virus in wastewater. Officials eager to lift pandemic restrictions, so their tourism industry could be re-energized, were looking for an early warning as to whether the disease was on the rebound. Their wastewater surveillance program has now been expanded to cover more than half the country's citizens.
Testing Wastewater to Detect the Spread of COVID-19
Tyrolean health authorities began their wastewater surveillance program in May 2020. The program was a success because it triggered early alerts to the presence of the disease and provided an independent confirmation about its prevalence.
Monitoring of 5,270 samples from forty-three sites was reported by the end of July 2021. Daleiden et al., from the Medical University of Innsbruck and State Institute for Integrated Care Tyrol, found that the sample tests detected outcrops of the disease and confirmed when it was absent. This experience showed that using national wastewater monitoring was an effective monitoring approach, in tandem with other forms of diagnostic testing.
Why Do Officials Test Wastewater?
Testing wastewater allows scientists to inexpensively look for infections like COVID-19 in large groups of people—up to millions—without resorting to the case-by-case basis of individual nose swabs. Scientists test wastewater samples for traces of disease shed in human feces and urine, which are then flushed into the sewer system. Sample data can be used to determine where cases might surge. Studying the samples for genetic or DNA sequences can also help scientists understand how the disease changes over time.
“Scientists test wastewater samples for traces of diseases shed in human feces and urine, … [and studying] the samples for genetic or DNA sequences can also help scientists understand how the disease changes over time.”
Dozens of Countries Using Wastewater Surveillance
For the first couple of years of the pandemic, two countries—Australia and New Zealand—reported almost no COVID-19 cases. They used wastewater monitoring in their zero-COVID-19 approach, and if a positive sample was discovered, officials increased testing, informed the public of the threat, and imposed restrictions where the virus was found.
Now fifty-eight countries have begun similar projects—known as wastewater-based epidemiology (WBE)—for SARS-CoV-2.
Countries using WBE include Finland, Hungary, Luxembourg, Spain, and Turkey. Regional monitoring programs exist in the U.S., the U.K., Australia, Canada, France, and Switzerland. Brazil and South Africa set up wastewater surveillance panels to show results for weekly regional monitoring.
How Does Wastewater Surveillance Work?
Testing wastewater samples for infectious diseases can be a cost-effective and reliable means of tracking a particular community's incidence of illness.
History provides a lesson as to its effectiveness. For example, it has successfully tracked polio and gastrointestinal disease.
Also, information is available within a week after the effluent enters the waste stream. Here's how it works:
People flush their germ-laden feces down their toilets.
The feces make its way through the sewer system.
Once the wastewater plant is reached, technicians test untreated wastewater samples for the presence and level of a pathogen.
Public health officials receive test reports and consider disease trends to decide where to set up mobile testing sites and vaccination clinics.
The Advantages and Limitations of Wastewater Surveillance
There are several additional advantages of wastewater surveillance for SARS-CoV-2. For example, it:
Is cost- and time- efficient.
Is not dependent on other COVID-19 testing.
Samples “all” people, not just those seen in healthcare setting.
Is feasible to implement in the US, since nearly 80% of US households are served by sewer systems.
While employing wastewater surveillance is relatively easy, it does have limitations. For example:
Wastewater surveillance is not available in areas without sewer systems.
It excludes samples from large hospitals, prisons, and universities with their own treatment plants.
Rainfall, industrial discharge, and animal waste can dilute or contaminate samples.
It cannot easily find low levels of the virus.
Because of these limitations, wastewater surveillance should augment, rather than replace, more time-intensive and costly methods, such as testing individuals through nose swabs.
China and COVID-19
One study noted that China had not created a national WBE system for early-detection of COVID-19, but was considering it. One concern was that China’s sewage system pipeline is “unbalanced” or offers incomplete coverage, the study said.
Along with Australia and New Zealand, China also implemented a “zero covid” policy and adhered to it for three years. However, in light of recent protests over the policy's limitations, China relaxed its restrictions. Officially, the country reported that the spread has peaked, although officials in other countries doubt that assertion. The disease is believed to be spreading there; however, it is hard to know the number of affected citizens.
Officials are also worried about the emergence of a new variant. As a result, European countries, Japan, South Korea, and the U.S., require extra screenings for people arriving from China. Notably, CDC spokeswoman Kristen Nordlund stated in an email to Reuters how the CDC is considering airplane wastewater analysis as an option.
Using Wastewater Surveillance to Detect New Infectious Diseases
A new report published by the U.S. National Academies of Sciences, Engineering, and Medicine recommended standardizing a wastewater surveillance system. A standardized system offers the hope of economic viability with the capacity of tracking multiple pathogens simultaneously. The report stresses the importance of various organizations cooperating to have a complete picture of a newly emerging disease. In addition, it recommends going beyond the current volunteer nature of wastewater surveillance toward a plan where roles are standardized and federal investments are feasible.
At least three well-known health organizations, the European Commission, U.S. Centers for Disease Control and Prevention, and the World Health Organization (WHO), recognized the potential in worldwide wastewater monitoring for pandemic management. Because of this, wastewater monitoring programs were established around the globe.
As of January 27, 2023, the WHO estimates there have been more than 752 million confirmed COVID-19 cases worldwide. There have been nearly seven million deaths attributed to COVID-19. The sense of urgency is imperative due to impacts of this highly contagious disease on public health and the worldwide economy.
Clearly, COVID-19 and its variants aren't going away anytime soon, which is all the more reason to continue refining the wastewater monitoring process, bring it to areas not being tested, and combine it with other public health data. Once standardized wastewater surveillance methods are available globally, perhaps the incidence of pandemics will be reduced.
*Cassie Journigan is a writer who lives in the north-central region of Florida in the United States. She focuses on issues related to sustainability. She is passionate about numerous topics including the Earth’s changing climate, pollution, social justice, and cross-cultural communications.